content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   * 
   *      http://www.apache.org/licenses/LICENSE-2.0
   * 
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.io;
  
  import java.io.BufferedOutputStream;
  import java.io.File;
  import java.io.FileFilter;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.OutputStream;
  import java.io.Reader;
  import java.io.UnsupportedEncodingException;
  import java.math.BigInteger;
  import java.net.URL;
  import java.net.URLConnection;
  import java.nio.ByteBuffer;
  import java.nio.channels.FileChannel;
  import java.nio.charset.Charset;
  import java.nio.charset.UnsupportedCharsetException;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Date;
  import java.util.Iterator;
  import java.util.List;
  import java.util.zip.CRC32;
  import java.util.zip.CheckedInputStream;
  import java.util.zip.Checksum;
  
  import org.apache.commons.io.filefilter.DirectoryFileFilter;
  import org.apache.commons.io.filefilter.FalseFileFilter;
  import org.apache.commons.io.filefilter.FileFilterUtils;
  import org.apache.commons.io.filefilter.IOFileFilter;
  import org.apache.commons.io.filefilter.SuffixFileFilter;
  import org.apache.commons.io.filefilter.TrueFileFilter;
  import org.apache.commons.io.output.NullOutputStream;
  
  /**
   * General file manipulation utilities.
   * <p>
   * Facilities are provided in the following areas:
   * <ul>
   * <li>writing to a file
   * <li>reading from a file
   * <li>make a directory including parent directories
   * <li>copying files and directories
   * <li>deleting files and directories
   * <li>converting to and from a URL
   * <li>listing files and directories by filter and extension
   * <li>comparing file content
   * <li>file last changed date
   * <li>calculating a checksum
   * </ul>
   * <p>
   * Origin of code: Excalibur, Alexandria, Commons-Utils
   *
   * @version $Id: FileUtils.java 1349509 2012-06-12 20:39:23Z ggregory $
   */
  public class FileUtils {
  
      /**
       * Instances should NOT be constructed in standard programming.
       */
      public FileUtils() {
          super();
      }
  
      /**
       * The number of bytes in a kilobyte.
       */
      public static final long ONE_KB = 1024;
  
      /**
       * The number of bytes in a kilobyte.
       * 
       * @since 2.4
       */
      public static final BigInteger ONE_KB_BI = BigInteger.valueOf(ONE_KB);
  
      /**
       * The number of bytes in a megabyte.
       */
      public static final long ONE_MB = ONE_KB * ONE_KB;
  
      /**
       * The number of bytes in a megabyte.
       * 
       * @since 2.4
       */
      public static final BigInteger ONE_MB_BI = ONE_KB_BI.multiply(ONE_KB_BI);
  
      /**
       * The file copy buffer size (30 MB)
       */
      private static final long FILE_COPY_BUFFER_SIZE = ONE_MB * 30;
  
      /**
       * The number of bytes in a gigabyte.
       */
      public static final long ONE_GB = ONE_KB * ONE_MB;
  
      /**
       * The number of bytes in a gigabyte.
       * 
       * @since 2.4
       */
      public static final BigInteger ONE_GB_BI = ONE_KB_BI.multiply(ONE_MB_BI);
  
      /**
       * The number of bytes in a terabyte.
       */
      public static final long ONE_TB = ONE_KB * ONE_GB;
  
      /**
       * The number of bytes in a terabyte.
       * 
       * @since 2.4
       */
      public static final BigInteger ONE_TB_BI = ONE_KB_BI.multiply(ONE_GB_BI);
  
      /**
       * The number of bytes in a petabyte.
       */
      public static final long ONE_PB = ONE_KB * ONE_TB;
  
      /**
       * The number of bytes in a petabyte.
       * 
       * @since 2.4
       */
      public static final BigInteger ONE_PB_BI = ONE_KB_BI.multiply(ONE_TB_BI);
  
      /**
       * The number of bytes in an exabyte.
       */
      public static final long ONE_EB = ONE_KB * ONE_PB;
  
      /**
       * The number of bytes in an exabyte.
       * 
       * @since 2.4
       */
      public static final BigInteger ONE_EB_BI = ONE_KB_BI.multiply(ONE_PB_BI);
  
      /**
       * The number of bytes in a zettabyte.
       */
      public static final BigInteger ONE_ZB = BigInteger.valueOf(ONE_KB).multiply(BigInteger.valueOf(ONE_EB));
  
      /**
       * The number of bytes in a yottabyte.
       */
      public static final BigInteger ONE_YB = ONE_KB_BI.multiply(ONE_ZB);
  
      /**
       * An empty array of type <code>File</code>.
       */
      public static final File[] EMPTY_FILE_ARRAY = new File[0];
  
      /**
       * The UTF-8 character set, used to decode octets in URLs.
       */
      private static final Charset UTF8 = Charset.forName("UTF-8");
  
      //-----------------------------------------------------------------------
      /**
       * Construct a file from the set of name elements.
       * 
       * @param directory the parent directory
       * @param names the name elements
       * @return the file
       * @since 2.1
       */
      public static File getFile(File directory, String... names) {
          if (directory == null) {
              throw new NullPointerException("directorydirectory must not be null");
          }
          if (names == null) {
              throw new NullPointerException("names must not be null");
          }
          File file = directory;
          for (String name : names) {
              file = new File(file, name);
          }
          return file;
      }
  
      /**
       * Construct a file from the set of name elements.
       * 
       * @param names the name elements
       * @return the file
       * @since 2.1
       */
      public static File getFile(String... names) {
          if (names == null) {
              throw new NullPointerException("names must not be null");
          }
          File file = null;
          for (String name : names) {
              if (file == null) {
                  file = new File(name);
              } else {
                  file = new File(file, name);
              }
          }
          return file;
      }
  
      /**
       * Returns the path to the system temporary directory.
       * 
       * @return the path to the system temporary directory.
       * 
       * @since 2.0
       */
      public static String getTempDirectoryPath() {
          return System.getProperty("java.io.tmpdir");
      }
      
      /**
       * Returns a {@link File} representing the system temporary directory.
       * 
       * @return the system temporary directory. 
       * 
       * @since 2.0
       */
      public static File getTempDirectory() {
          return new File(getTempDirectoryPath());
      }
      
      /**
       * Returns the path to the user's home directory.
       * 
       * @return the path to the user's home directory.
       * 
       * @since 2.0
       */
      public static String getUserDirectoryPath() {
          return System.getProperty("user.home");
      }
      
      /**
       * Returns a {@link File} representing the user's home directory.
       * 
       * @return the user's home directory.
       * 
       * @since 2.0
       */
      public static File getUserDirectory() {
          return new File(getUserDirectoryPath());
      }
      
      //-----------------------------------------------------------------------
      /**
       * Opens a {@link FileInputStream} for the specified file, providing better
       * error messages than simply calling <code>new FileInputStream(file)</code>.
       * <p>
       * At the end of the method either the stream will be successfully opened,
       * or an exception will have been thrown.
       * <p>
       * An exception is thrown if the file does not exist.
       * An exception is thrown if the file object exists but is a directory.
       * An exception is thrown if the file exists but cannot be read.
       * 
       * @param file  the file to open for input, must not be {@code null}
       * @return a new {@link FileInputStream} for the specified file
       * @throws FileNotFoundException if the file does not exist
       * @throws IOException if the file object is a directory
       * @throws IOException if the file cannot be read
       * @since 1.3
       */
      public static FileInputStream openInputStream(File file) throws IOException {
          if (file.exists()) {
              if (file.isDirectory()) {
                  throw new IOException("File '" + file + "' exists but is a directory");
              }
              if (file.canRead() == false) {
                  throw new IOException("File '" + file + "' cannot be read");
              }
          } else {
              throw new FileNotFoundException("File '" + file + "' does not exist");
          }
          return new FileInputStream(file);
      }
  
      //-----------------------------------------------------------------------
      /**
       * Opens a {@link FileOutputStream} for the specified file, checking and
       * creating the parent directory if it does not exist.
       * <p>
       * At the end of the method either the stream will be successfully opened,
       * or an exception will have been thrown.
       * <p>
       * The parent directory will be created if it does not exist.
       * The file will be created if it does not exist.
       * An exception is thrown if the file object exists but is a directory.
       * An exception is thrown if the file exists but cannot be written to.
       * An exception is thrown if the parent directory cannot be created.
       * 
       * @param file  the file to open for output, must not be {@code null}
       * @return a new {@link FileOutputStream} for the specified file
       * @throws IOException if the file object is a directory
       * @throws IOException if the file cannot be written to
       * @throws IOException if a parent directory needs creating but that fails
       * @since 1.3
       */
      public static FileOutputStream openOutputStream(File file) throws IOException {
          return openOutputStream(file, false);
      }
  
      /**
       * Opens a {@link FileOutputStream} for the specified file, checking and
       * creating the parent directory if it does not exist.
       * <p>
       * At the end of the method either the stream will be successfully opened,
       * or an exception will have been thrown.
       * <p>
       * The parent directory will be created if it does not exist.
       * The file will be created if it does not exist.
       * An exception is thrown if the file object exists but is a directory.
       * An exception is thrown if the file exists but cannot be written to.
       * An exception is thrown if the parent directory cannot be created.
       * 
       * @param file  the file to open for output, must not be {@code null}
       * @param append if {@code true}, then bytes will be added to the
       * end of the file rather than overwriting
       * @return a new {@link FileOutputStream} for the specified file
       * @throws IOException if the file object is a directory
       * @throws IOException if the file cannot be written to
       * @throws IOException if a parent directory needs creating but that fails
       * @since 2.1
       */
      public static FileOutputStream openOutputStream(File file, boolean append) throws IOException {
          if (file.exists()) {
              if (file.isDirectory()) {
                  throw new IOException("File '" + file + "' exists but is a directory");
              }
              if (file.canWrite() == false) {
                  throw new IOException("File '" + file + "' cannot be written to");
              }
          } else {
              File parent = file.getParentFile();
              if (parent != null) {
                  if (!parent.mkdirs() && !parent.isDirectory()) {
                      throw new IOException("Directory '" + parent + "' could not be created");
                  }
              }
          }
          return new FileOutputStream(file, append);
      }
  
      //-----------------------------------------------------------------------
      /**
       * Returns a human-readable version of the file size, where the input represents a specific number of bytes.
       * <p>
       * If the size is over 1GB, the size is returned as the number of whole GB, i.e. the size is rounded down to the
       * nearest GB boundary.
       * </p>
       * <p>
       * Similarly for the 1MB and 1KB boundaries.
       * </p>
       * 
       * @param size
       *            the number of bytes
       * @return a human-readable display value (includes units - EB, PB, TB, GB, MB, KB or bytes)
       * @see <a href="https://issues.apache.org/jira/browse/IO-226">IO-226 - should the rounding be changed?</a>
       * @since 2.4
       */
      // See https://issues.apache.org/jira/browse/IO-226 - should the rounding be changed?
      public static String byteCountToDisplaySize(BigInteger size) {
          String displaySize;
  
          if (size.divide(ONE_EB_BI).compareTo(BigInteger.ZERO) > 0) {
              displaySize = String.valueOf(size.divide(ONE_EB_BI)) + " EB";
          } else if (size.divide(ONE_PB_BI).compareTo(BigInteger.ZERO) > 0) {
              displaySize = String.valueOf(size.divide(ONE_PB_BI)) + " PB";
          } else if (size.divide(ONE_TB_BI).compareTo(BigInteger.ZERO) > 0) {
              displaySize = String.valueOf(size.divide(ONE_TB_BI)) + " TB";
          } else if (size.divide(ONE_GB_BI).compareTo(BigInteger.ZERO) > 0) {
              displaySize = String.valueOf(size.divide(ONE_GB_BI)) + " GB";
          } else if (size.divide(ONE_MB_BI).compareTo(BigInteger.ZERO) > 0) {
              displaySize = String.valueOf(size.divide(ONE_MB_BI)) + " MB";
          } else if (size.divide(ONE_KB_BI).compareTo(BigInteger.ZERO) > 0) {
              displaySize = String.valueOf(size.divide(ONE_KB_BI)) + " KB";
          } else {
              displaySize = String.valueOf(size) + " bytes";
          }
          return displaySize;
      }
  
      /**
       * Returns a human-readable version of the file size, where the input represents a specific number of bytes.
       * <p>
       * If the size is over 1GB, the size is returned as the number of whole GB, i.e. the size is rounded down to the
       * nearest GB boundary.
       * </p>
       * <p>
       * Similarly for the 1MB and 1KB boundaries.
       * </p>
       * 
       * @param size
       *            the number of bytes
       * @return a human-readable display value (includes units - EB, PB, TB, GB, MB, KB or bytes)
       * @see <a href="https://issues.apache.org/jira/browse/IO-226">IO-226 - should the rounding be changed?</a>
       */
      // See https://issues.apache.org/jira/browse/IO-226 - should the rounding be changed?
      public static String byteCountToDisplaySize(long size) {
          return byteCountToDisplaySize(BigInteger.valueOf(size));
      }
  
      //-----------------------------------------------------------------------
      /**
       * Implements the same behaviour as the "touch" utility on Unix. It creates
       * a new file with size 0 or, if the file exists already, it is opened and
       * closed without modifying it, but updating the file date and time.
       * <p>
       * NOTE: As from v1.3, this method throws an IOException if the last
       * modified date of the file cannot be set. Also, as from v1.3 this method
       * creates parent directories if they do not exist.
       *
       * @param file  the File to touch
       * @throws IOException If an I/O problem occurs
       */
      public static void touch(File file) throws IOException {
          if (!file.exists()) {
              OutputStream out = openOutputStream(file);
              IOUtils.closeQuietly(out);
          }
          boolean success = file.setLastModified(System.currentTimeMillis());
          if (!success) {
              throw new IOException("Unable to set the last modification time for " + file);
          }
      }
  
      //-----------------------------------------------------------------------
      /**
       * Converts a Collection containing java.io.File instanced into array
       * representation. This is to account for the difference between
       * File.listFiles() and FileUtils.listFiles().
       *
       * @param files  a Collection containing java.io.File instances
       * @return an array of java.io.File
       */
      public static File[] convertFileCollectionToFileArray(Collection<File> files) {
           return files.toArray(new File[files.size()]);
      }
  
      //-----------------------------------------------------------------------
      /**
       * Finds files within a given directory (and optionally its
       * subdirectories). All files found are filtered by an IOFileFilter.
       *
       * @param files the collection of files found.
       * @param directory the directory to search in.
       * @param filter the filter to apply to files and directories.
       * @param includeSubDirectories indicates if will include the subdirectories themselves
       */
      private static void innerListFiles(Collection<File> files, File directory,
              IOFileFilter filter, boolean includeSubDirectories) {
          File[] found = directory.listFiles((FileFilter) filter);
          
          if (found != null) {
              for (File file : found) {
                  if (file.isDirectory()) {
                      if (includeSubDirectories) {
                          files.add(file);
                      }
                      innerListFiles(files, file, filter, includeSubDirectories);
                  } else {
                      files.add(file);
                  }
              }
          }
      }
  
      /**
       * Finds files within a given directory (and optionally its
       * subdirectories). All files found are filtered by an IOFileFilter.
       * <p>
       * If your search should recurse into subdirectories you can pass in
       * an IOFileFilter for directories. You don't need to bind a
       * DirectoryFileFilter (via logical AND) to this filter. This method does
       * that for you.
       * <p>
       * An example: If you want to search through all directories called
       * "temp" you pass in <code>FileFilterUtils.NameFileFilter("temp")</code>
       * <p>
       * Another common usage of this method is find files in a directory
       * tree but ignoring the directories generated CVS. You can simply pass
       * in <code>FileFilterUtils.makeCVSAware(null)</code>.
       *
       * @param directory  the directory to search in
       * @param fileFilter  filter to apply when finding files.
       * @param dirFilter  optional filter to apply when finding subdirectories.
       * If this parameter is {@code null}, subdirectories will not be included in the
       * search. Use TrueFileFilter.INSTANCE to match all directories.
       * @return an collection of java.io.File with the matching files
       * @see org.apache.commons.io.filefilter.FileFilterUtils
       * @see org.apache.commons.io.filefilter.NameFileFilter
       */
      public static Collection<File> listFiles(
              File directory, IOFileFilter fileFilter, IOFileFilter dirFilter) {
          validateListFilesParameters(directory, fileFilter);
  
          IOFileFilter effFileFilter = setUpEffectiveFileFilter(fileFilter);
          IOFileFilter effDirFilter = setUpEffectiveDirFilter(dirFilter);
  
          //Find files
          Collection<File> files = new java.util.LinkedList<File>();
          innerListFiles(files, directory,
              FileFilterUtils.or(effFileFilter, effDirFilter), false);
          return files;
      }
  
      /**
       * Validates the given arguments.
       * <ul>
       * <li>Throws {@link IllegalArgumentException} if {@code directory} is not a directory</li>
       * <li>Throws {@link NullPointerException} if {@code fileFilter} is null</li>
       * </ul>
       * 
       * @param directory The File to test
       * @param fileFilter The IOFileFilter to test
       */
      private static void validateListFilesParameters(File directory, IOFileFilter fileFilter) {
          if (!directory.isDirectory()) {
              throw new IllegalArgumentException("Parameter 'directory' is not a directory");
          }
          if (fileFilter == null) {
              throw new NullPointerException("Parameter 'fileFilter' is null");
          }
      }
  
      /**
       * Returns a filter that accepts files in addition to the {@link File} objects accepted by the given filter.
       * 
       * @param fileFilter a base filter to add to
       * @return a filter that accepts files 
       */
      private static IOFileFilter setUpEffectiveFileFilter(IOFileFilter fileFilter) {
          return FileFilterUtils.and(fileFilter, FileFilterUtils.notFileFilter(DirectoryFileFilter.INSTANCE));
      }
  
      /**
       * Returns a filter that accepts directories in addition to the {@link File} objects accepted by the given filter.
       * 
       * @param dirFilter a base filter to add to
       * @return a filter that accepts directories 
       */
      private static IOFileFilter setUpEffectiveDirFilter(IOFileFilter dirFilter) {
          return dirFilter == null ? FalseFileFilter.INSTANCE : FileFilterUtils.and(dirFilter,
                  DirectoryFileFilter.INSTANCE);
      }
  
      /**
       * Finds files within a given directory (and optionally its
       * subdirectories). All files found are filtered by an IOFileFilter.
       * <p>
       * The resulting collection includes the subdirectories themselves.
       * <p>
       * @see org.apache.commons.io.FileUtils#listFiles  
       *
       * @param directory  the directory to search in
       * @param fileFilter  filter to apply when finding files.
       * @param dirFilter  optional filter to apply when finding subdirectories.
       * If this parameter is {@code null}, subdirectories will not be included in the
       * search. Use TrueFileFilter.INSTANCE to match all directories.
       * @return an collection of java.io.File with the matching files
       * @see org.apache.commons.io.filefilter.FileFilterUtils
       * @see org.apache.commons.io.filefilter.NameFileFilter
       * @since 2.2
       */
      public static Collection<File> listFilesAndDirs(
              File directory, IOFileFilter fileFilter, IOFileFilter dirFilter) {
          validateListFilesParameters(directory, fileFilter);
  
          IOFileFilter effFileFilter = setUpEffectiveFileFilter(fileFilter);
          IOFileFilter effDirFilter = setUpEffectiveDirFilter(dirFilter);
  
          //Find files
          Collection<File> files = new java.util.LinkedList<File>();
          if (directory.isDirectory()) {
              files.add(directory);
          }
          innerListFiles(files, directory,
              FileFilterUtils.or(effFileFilter, effDirFilter), true);
          return files;
      }
  
      /**
       * Allows iteration over the files in given directory (and optionally
       * its subdirectories).
       * <p>
       * All files found are filtered by an IOFileFilter. This method is
       * based on {@link #listFiles(File, IOFileFilter, IOFileFilter)},
       * which supports Iterable ('foreach' loop).
       * <p>
       * @param directory  the directory to search in
       * @param fileFilter  filter to apply when finding files.
       * @param dirFilter  optional filter to apply when finding subdirectories.
       * If this parameter is {@code null}, subdirectories will not be included in the
       * search. Use TrueFileFilter.INSTANCE to match all directories.
       * @return an iterator of java.io.File for the matching files
       * @see org.apache.commons.io.filefilter.FileFilterUtils
       * @see org.apache.commons.io.filefilter.NameFileFilter
       * @since 1.2
       */
      public static Iterator<File> iterateFiles(
              File directory, IOFileFilter fileFilter, IOFileFilter dirFilter) {
          return listFiles(directory, fileFilter, dirFilter).iterator();
      }
  
      /**
       * Allows iteration over the files in given directory (and optionally
       * its subdirectories).
       * <p>
       * All files found are filtered by an IOFileFilter. This method is
       * based on {@link #listFilesAndDirs(File, IOFileFilter, IOFileFilter)},
       * which supports Iterable ('foreach' loop).
       * <p>
       * The resulting iterator includes the subdirectories themselves.
       * 
       * @param directory  the directory to search in
       * @param fileFilter  filter to apply when finding files.
       * @param dirFilter  optional filter to apply when finding subdirectories.
       * If this parameter is {@code null}, subdirectories will not be included in the
       * search. Use TrueFileFilter.INSTANCE to match all directories.
       * @return an iterator of java.io.File for the matching files
       * @see org.apache.commons.io.filefilter.FileFilterUtils
       * @see org.apache.commons.io.filefilter.NameFileFilter
       * @since 2.2
       */
      public static Iterator<File> iterateFilesAndDirs(File directory, IOFileFilter fileFilter, IOFileFilter dirFilter) {
          return listFilesAndDirs(directory, fileFilter, dirFilter).iterator();
      }
  
      //-----------------------------------------------------------------------
      /**
       * Converts an array of file extensions to suffixes for use
       * with IOFileFilters.
       *
       * @param extensions  an array of extensions. Format: {"java", "xml"}
       * @return an array of suffixes. Format: {".java", ".xml"}
       */
      private static String[] toSuffixes(String[] extensions) {
          String[] suffixes = new String[extensions.length];
          for (int i = 0; i < extensions.length; i++) {
              suffixes[i] = "." + extensions[i];
          }
          return suffixes;
      }
  
  
      /**
       * Finds files within a given directory (and optionally its subdirectories)
       * which match an array of extensions.
       *
       * @param directory  the directory to search in
       * @param extensions  an array of extensions, ex. {"java","xml"}. If this
       * parameter is {@code null}, all files are returned.
       * @param recursive  if true all subdirectories are searched as well
       * @return an collection of java.io.File with the matching files
       */
      public static Collection<File> listFiles(
              File directory, String[] extensions, boolean recursive) {
          IOFileFilter filter;
          if (extensions == null) {
              filter = TrueFileFilter.INSTANCE;
          } else {
              String[] suffixes = toSuffixes(extensions);
              filter = new SuffixFileFilter(suffixes);
          }
          return listFiles(directory, filter,
              recursive ? TrueFileFilter.INSTANCE : FalseFileFilter.INSTANCE);
      }
  
      /**
       * Allows iteration over the files in a given directory (and optionally
       * its subdirectories) which match an array of extensions. This method
       * is based on {@link #listFiles(File, String[], boolean)},
       * which supports Iterable ('foreach' loop).
       *
       * @param directory  the directory to search in
       * @param extensions  an array of extensions, ex. {"java","xml"}. If this
       * parameter is {@code null}, all files are returned.
       * @param recursive  if true all subdirectories are searched as well
       * @return an iterator of java.io.File with the matching files
       * @since 1.2
       */
      public static Iterator<File> iterateFiles(
              File directory, String[] extensions, boolean recursive) {
          return listFiles(directory, extensions, recursive).iterator();
      }
  
      //-----------------------------------------------------------------------
      /**
       * Compares the contents of two files to determine if they are equal or not.
       * <p>
       * This method checks to see if the two files are different lengths
       * or if they point to the same file, before resorting to byte-by-byte
       * comparison of the contents.
       * <p>
       * Code origin: Avalon
       *
       * @param file1  the first file
       * @param file2  the second file
       * @return true if the content of the files are equal or they both don't
       * exist, false otherwise
       * @throws IOException in case of an I/O error
       */
      public static boolean contentEquals(File file1, File file2) throws IOException {
          boolean file1Exists = file1.exists();
          if (file1Exists != file2.exists()) {
              return false;
          }
  
          if (!file1Exists) {
              // two not existing files are equal
              return true;
          }
  
          if (file1.isDirectory() || file2.isDirectory()) {
              // don't want to compare directory contents
              throw new IOException("Can't compare directories, only files");
          }
  
          if (file1.length() != file2.length()) {
              // lengths differ, cannot be equal
              return false;
          }
  
          if (file1.getCanonicalFile().equals(file2.getCanonicalFile())) {
              // same file
              return true;
          }
  
          InputStream input1 = null;
          InputStream input2 = null;
          try {
              input1 = new FileInputStream(file1);
              input2 = new FileInputStream(file2);
              return IOUtils.contentEquals(input1, input2);
  
          } finally {
              IOUtils.closeQuietly(input1);
              IOUtils.closeQuietly(input2);
          }
      }
  
      //-----------------------------------------------------------------------
      /**
       * Compares the contents of two files to determine if they are equal or not.
       * <p>
       * This method checks to see if the two files point to the same file, 
       * before resorting to line-by-line comparison of the contents.
       * <p>
       *
       * @param file1  the first file
       * @param file2  the second file
       * @param charsetName the character encoding to be used. 
       *        May be null, in which case the platform default is used
       * @return true if the content of the files are equal or neither exists,
       *         false otherwise
       * @throws IOException in case of an I/O error
       * @since 2.2
       * @see IOUtils#contentEqualsIgnoreEOL(Reader, Reader)
       */
      public static boolean contentEqualsIgnoreEOL(File file1, File file2, String charsetName) throws IOException {
          boolean file1Exists = file1.exists();
          if (file1Exists != file2.exists()) {
              return false;
          }
  
          if (!file1Exists) {
              // two not existing files are equal
              return true;
          }
  
          if (file1.isDirectory() || file2.isDirectory()) {
              // don't want to compare directory contents
              throw new IOException("Can't compare directories, only files");
          }
  
          if (file1.getCanonicalFile().equals(file2.getCanonicalFile())) {
              // same file
              return true;
          }
  
          Reader input1 = null;
          Reader input2 = null;
          try {
              if (charsetName == null) {
                  input1 = new InputStreamReader(new FileInputStream(file1));
                  input2 = new InputStreamReader(new FileInputStream(file2));
              } else {
                  input1 = new InputStreamReader(new FileInputStream(file1), charsetName);
                  input2 = new InputStreamReader(new FileInputStream(file2), charsetName);
              }
              return IOUtils.contentEqualsIgnoreEOL(input1, input2);
  
          } finally {
              IOUtils.closeQuietly(input1);
              IOUtils.closeQuietly(input2);
          }
      }
  
      //-----------------------------------------------------------------------
      /**
       * Convert from a <code>URL</code> to a <code>File</code>.
       * <p>
       * From version 1.1 this method will decode the URL.
       * Syntax such as <code>file:///my%20docs/file.txt</code> will be
       * correctly decoded to <code>/my docs/file.txt</code>. Starting with version
       * 1.5, this method uses UTF-8 to decode percent-encoded octets to characters.
       * Additionally, malformed percent-encoded octets are handled leniently by
       * passing them through literally.
       *
       * @param url  the file URL to convert, {@code null} returns {@code null}
       * @return the equivalent <code>File</code> object, or {@code null}
       *  if the URL's protocol is not <code>file</code>
       */
      public static File toFile(URL url) {
          if (url == null || !"file".equalsIgnoreCase(url.getProtocol())) {
              return null;
          } else {
              String filename = url.getFile().replace('/', File.separatorChar);
              filename = decodeUrl(filename);
              return new File(filename);
          }
      }
  
      /**
       * Decodes the specified URL as per RFC 3986, i.e. transforms
       * percent-encoded octets to characters by decoding with the UTF-8 character
       * set. This function is primarily intended for usage with
       * {@link java.net.URL} which unfortunately does not enforce proper URLs. As
       * such, this method will leniently accept invalid characters or malformed
       * percent-encoded octets and simply pass them literally through to the
       * result string. Except for rare edge cases, this will make unencoded URLs
       * pass through unaltered.
       * 
       * @param url  The URL to decode, may be {@code null}.
       * @return The decoded URL or {@code null} if the input was
       *         {@code null}.
       */
      static String decodeUrl(String url) {
          String decoded = url;
          if (url != null && url.indexOf('%') >= 0) {
              int n = url.length();
              StringBuffer buffer = new StringBuffer();
              ByteBuffer bytes = ByteBuffer.allocate(n);
              for (int i = 0; i < n;) {
                  if (url.charAt(i) == '%') {
                      try {
                          do {
                              byte octet = (byte) Integer.parseInt(url.substring(i + 1, i + 3), 16);
                              bytes.put(octet);
                              i += 3;
                          } while (i < n && url.charAt(i) == '%');
                          continue;
                      } catch (RuntimeException e) {
                          // malformed percent-encoded octet, fall through and
                          // append characters literally
                      } finally {
                          if (bytes.position() > 0) {
                              bytes.flip();
                              buffer.append(UTF8.decode(bytes).toString());
                              bytes.clear();
                          }
                      }
                  }
                  buffer.append(url.charAt(i++));
              }
              decoded = buffer.toString();
          }
          return decoded;
      }
  
      /**
       * Converts each of an array of <code>URL</code> to a <code>File</code>.
       * <p>
       * Returns an array of the same size as the input.
       * If the input is {@code null}, an empty array is returned.
       * If the input contains {@code null}, the output array contains {@code null} at the same
       * index.
       * <p>
       * This method will decode the URL.
       * Syntax such as <code>file:///my%20docs/file.txt</code> will be
       * correctly decoded to <code>/my docs/file.txt</code>.
       *
       * @param urls  the file URLs to convert, {@code null} returns empty array
       * @return a non-{@code null} array of Files matching the input, with a {@code null} item
       *  if there was a {@code null} at that index in the input array
       * @throws IllegalArgumentException if any file is not a URL file
       * @throws IllegalArgumentException if any file is incorrectly encoded
       * @since 1.1
       */
      public static File[] toFiles(URL[] urls) {
          if (urls == null || urls.length == 0) {
              return EMPTY_FILE_ARRAY;
          }
          File[] files = new File[urls.length];
          for (int i = 0; i < urls.length; i++) {
              URL url = urls[i];
              if (url != null) {
                  if (url.getProtocol().equals("file") == false) {
                      throw new IllegalArgumentException(
                              "URL could not be converted to a File: " + url);
                  }
                  files[i] = toFile(url);
              }
          }
          return files;
      }
  
      /**
       * Converts each of an array of <code>File</code> to a <code>URL</code>.
       * <p>
       * Returns an array of the same size as the input.
       *
       * @param files  the files to convert, must not be {@code null}
       * @return an array of URLs matching the input
       * @throws IOException if a file cannot be converted
       * @throws NullPointerException if the parameter is null
       */
      public static URL[] toURLs(File[] files) throws IOException {
          URL[] urls = new URL[files.length];
  
          for (int i = 0; i < urls.length; i++) {
              urls[i] = files[i].toURI().toURL();
          }
  
          return urls;
      }
  
      //-----------------------------------------------------------------------
      /**
       * Copies a file to a directory preserving the file date.
       * <p>
       * This method copies the contents of the specified source file
       * to a file of the same name in the specified destination directory.
       * The destination directory is created if it does not exist.
       * If the destination file exists, then this method will overwrite it.
       * <p>
       * <strong>Note:</strong> This method tries to preserve the file's last
       * modified date/times using {@link File#setLastModified(long)}, however
       * it is not guaranteed that the operation will succeed.
       * If the modification operation fails, no indication is provided.
       *
       * @param srcFile  an existing file to copy, must not be {@code null}
       * @param destDir  the directory to place the copy in, must not be {@code null}
       *
       * @throws NullPointerException if source or destination is null
       * @throws IOException if source or destination is invalid
       * @throws IOException if an IO error occurs during copying
       * @see #copyFile(File, File, boolean)
       */
      public static void copyFileToDirectory(File srcFile, File destDir) throws IOException {
          copyFileToDirectory(srcFile, destDir, true);
      }
  
      /**
       * Copies a file to a directory optionally preserving the file date.
       * <p>
       * This method copies the contents of the specified source file
       * to a file of the same name in the specified destination directory.
       * The destination directory is created if it does not exist.
       * If the destination file exists, then this method will overwrite it.
       * <p>
       * <strong>Note:</strong> Setting <code>preserveFileDate</code> to
       * {@code true} tries to preserve the file's last modified
       * date/times using {@link File#setLastModified(long)}, however it is
       * not guaranteed that the operation will succeed.
       * If the modification operation fails, no indication is provided.
       *
       * @param srcFile  an existing file to copy, must not be {@code null}
       * @param destDir  the directory to place the copy in, must not be {@code null}
       * @param preserveFileDate  true if the file date of the copy
       *  should be the same as the original
       *
       * @throws NullPointerException if source or destination is {@code null}
       * @throws IOException if source or destination is invalid
       * @throws IOException if an IO error occurs during copying
       * @see #copyFile(File, File, boolean)
       * @since 1.3
       */
      public static void copyFileToDirectory(File srcFile, File destDir, boolean preserveFileDate) throws IOException {
          if (destDir == null) {
              throw new NullPointerException("Destination must not be null");
          }
          if (destDir.exists() && destDir.isDirectory() == false) {
              throw new IllegalArgumentException("Destination '" + destDir + "' is not a directory");
          }
          File destFile = new File(destDir, srcFile.getName());
          copyFile(srcFile, destFile, preserveFileDate);
      }
  
      /**
       * Copies a file to a new location preserving the file date.
       * <p>
       * This method copies the contents of the specified source file to the
       * specified destination file. The directory holding the destination file is
       * created if it does not exist. If the destination file exists, then this
       * method will overwrite it.
       * <p>
       * <strong>Note:</strong> This method tries to preserve the file's last
       * modified date/times using {@link File#setLastModified(long)}, however
       * it is not guaranteed that the operation will succeed.
       * If the modification operation fails, no indication is provided.
       * 
       * @param srcFile  an existing file to copy, must not be {@code null}
       * @param destFile  the new file, must not be {@code null}
       * 
       * @throws NullPointerException if source or destination is {@code null}
       * @throws IOException if source or destination is invalid
       * @throws IOException if an IO error occurs during copying
       * @see #copyFileToDirectory(File, File)
       */
      public static void copyFile(File srcFile, File destFile) throws IOException {
          copyFile(srcFile, destFile, true);
      }
  
      /**
       * Copies a file to a new location.
       * <p>
       * This method copies the contents of the specified source file
       * to the specified destination file.
       * The directory holding the destination file is created if it does not exist.
       * If the destination file exists, then this method will overwrite it.
       * <p>
       * <strong>Note:</strong> Setting <code>preserveFileDate</code> to
       * {@code true} tries to preserve the file's last modified
       * date/times using {@link File#setLastModified(long)}, however it is
       * not guaranteed that the operation will succeed.
       * If the modification operation fails, no indication is provided.
       *
       * @param srcFile  an existing file to copy, must not be {@code null}
       * @param destFile  the new file, must not be {@code null}
       * @param preserveFileDate  true if the file date of the copy
       *  should be the same as the original
       *
       * @throws NullPointerException if source or destination is {@code null}
       * @throws IOException if source or destination is invalid
       * @throws IOException if an IO error occurs during copying
       * @see #copyFileToDirectory(File, File, boolean)
       */
      public static void copyFile(File srcFile, File destFile,
              boolean preserveFileDate) throws IOException {
          if (srcFile == null) {
              throw new NullPointerException("Source must not be null");
          }
          if (destFile == null) {
              throw new NullPointerException("Destination must not be null");
          }
          if (srcFile.exists() == false) {
              throw new FileNotFoundException("Source '" + srcFile + "' does not exist");
          }
          if (srcFile.isDirectory()) {
              throw new IOException("Source '" + srcFile + "' exists but is a directory");
          }
          if (srcFile.getCanonicalPath().equals(destFile.getCanonicalPath())) {
              throw new IOException("Source '" + srcFile + "' and destination '" + destFile + "' are the same");
          }
          File parentFile = destFile.getParentFile();
          if (parentFile != null) {
              if (!parentFile.mkdirs() && !parentFile.isDirectory()) {
                  throw new IOException("Destination '" + parentFile + "' directory cannot be created");
              }
          }
          if (destFile.exists() && destFile.canWrite() == false) {
              throw new IOException("Destination '" + destFile + "' exists but is read-only");
          }
          doCopyFile(srcFile, destFile, preserveFileDate);
      }
  
      /**
       * Copy bytes from a <code>File</code> to an <code>OutputStream</code>.
       * <p>
       * This method buffers the input internally, so there is no need to use a <code>BufferedInputStream</code>.
       * </p>
       * 
       * @param input
       *            the <code>File</code> to read from
       * @param output
       *            the <code>OutputStream</code> to write to
       * @return the number of bytes copied
       * @throws NullPointerException
       *             if the input or output is null
       * @throws IOException
       *             if an I/O error occurs
       * @since 2.1
       */
      public static long copyFile(File input, OutputStream output) throws IOException {
          final FileInputStream fis = new FileInputStream(input);
          try {
              return IOUtils.copyLarge(fis, output);
          } finally {
              fis.close();
          }
      }
      
      /**
       * Internal copy file method.
       * 
       * @param srcFile  the validated source file, must not be {@code null}
       * @param destFile  the validated destination file, must not be {@code null}
       * @param preserveFileDate  whether to preserve the file date
       * @throws IOException if an error occurs
       */
      private static void doCopyFile(File srcFile, File destFile, boolean preserveFileDate) throws IOException {
          if (destFile.exists() && destFile.isDirectory()) {
              throw new IOException("Destination '" + destFile + "' exists but is a directory");
          }
  
          FileInputStream fis = null;
          FileOutputStream fos = null;
          FileChannel input = null;
          FileChannel output = null;
          try {
              fis = new FileInputStream(srcFile);
              fos = new FileOutputStream(destFile);
              input  = fis.getChannel();
              output = fos.getChannel();
              long size = input.size();
              long pos = 0;
              long count = 0;
              while (pos < size) {
                  count = size - pos > FILE_COPY_BUFFER_SIZE ? FILE_COPY_BUFFER_SIZE : size - pos;
                  pos += output.transferFrom(input, pos, count);
              }
          } finally {
              IOUtils.closeQuietly(output);
              IOUtils.closeQuietly(fos);
              IOUtils.closeQuietly(input);
              IOUtils.closeQuietly(fis);
          }
  
          if (srcFile.length() != destFile.length()) {
              throw new IOException("Failed to copy full contents from '" +
                      srcFile + "' to '" + destFile + "'");
          }
          if (preserveFileDate) {
              destFile.setLastModified(srcFile.lastModified());
          }
      }
  
      //-----------------------------------------------------------------------
      /**
       * Copies a directory to within another directory preserving the file dates.
       * <p>
       * This method copies the source directory and all its contents to a
       * directory of the same name in the specified destination directory.
       * <p>
       * The destination directory is created if it does not exist.
       * If the destination directory did exist, then this method merges
       * the source with the destination, with the source taking precedence.
       * <p>
       * <strong>Note:</strong> This method tries to preserve the files' last
       * modified date/times using {@link File#setLastModified(long)}, however
       * it is not guaranteed that those operations will succeed.
       * If the modification operation fails, no indication is provided.
       *
       * @param srcDir  an existing directory to copy, must not be {@code null}
       * @param destDir  the directory to place the copy in, must not be {@code null}
       *
       * @throws NullPointerException if source or destination is {@code null}
       * @throws IOException if source or destination is invalid
       * @throws IOException if an IO error occurs during copying
       * @since 1.2
       */
      public static void copyDirectoryToDirectory(File srcDir, File destDir) throws IOException {
          if (srcDir == null) {
              throw new NullPointerException("Source must not be null");
          }
          if (srcDir.exists() && srcDir.isDirectory() == false) {
              throw new IllegalArgumentException("Source '" + destDir + "' is not a directory");
          }
          if (destDir == null) {
              throw new NullPointerException("Destination must not be null");
          }
          if (destDir.exists() && destDir.isDirectory() == false) {
              throw new IllegalArgumentException("Destination '" + destDir + "' is not a directory");
          }
          copyDirectory(srcDir, new File(destDir, srcDir.getName()), true);
      }
  
      /**
       * Copies a whole directory to a new location preserving the file dates.
       * <p>
       * This method copies the specified directory and all its child
       * directories and files to the specified destination.
       * The destination is the new location and name of the directory.
       * <p>
       * The destination directory is created if it does not exist.
       * If the destination directory did exist, then this method merges
       * the source with the destination, with the source taking precedence.
       * <p>
       * <strong>Note:</strong> This method tries to preserve the files' last
       * modified date/times using {@link File#setLastModified(long)}, however
       * it is not guaranteed that those operations will succeed.
       * If the modification operation fails, no indication is provided.
       *
       * @param srcDir  an existing directory to copy, must not be {@code null}
       * @param destDir  the new directory, must not be {@code null}
       *
       * @throws NullPointerException if source or destination is {@code null}
       * @throws IOException if source or destination is invalid
       * @throws IOException if an IO error occurs during copying
       * @since 1.1
       */
      public static void copyDirectory(File srcDir, File destDir) throws IOException {
          copyDirectory(srcDir, destDir, true);
      }
  
      /**
       * Copies a whole directory to a new location.
       * <p>
       * This method copies the contents of the specified source directory
       * to within the specified destination directory.
       * <p>
       * The destination directory is created if it does not exist.
       * If the destination directory did exist, then this method merges
       * the source with the destination, with the source taking precedence.
       * <p>
       * <strong>Note:</strong> Setting <code>preserveFileDate</code> to
       * {@code true} tries to preserve the files' last modified
       * date/times using {@link File#setLastModified(long)}, however it is
       * not guaranteed that those operations will succeed.
       * If the modification operation fails, no indication is provided.
       *
       * @param srcDir  an existing directory to copy, must not be {@code null}
       * @param destDir  the new directory, must not be {@code null}
       * @param preserveFileDate  true if the file date of the copy
       *  should be the same as the original
       *
       * @throws NullPointerException if source or destination is {@code null}
       * @throws IOException if source or destination is invalid
       * @throws IOException if an IO error occurs during copying
       * @since 1.1
       */
      public static void copyDirectory(File srcDir, File destDir,
              boolean preserveFileDate) throws IOException {
          copyDirectory(srcDir, destDir, null, preserveFileDate);
      }
  
      /**
       * Copies a filtered directory to a new location preserving the file dates.
       * <p>
       * This method copies the contents of the specified source directory
       * to within the specified destination directory.
       * <p>
       * The destination directory is created if it does not exist.
       * If the destination directory did exist, then this method merges
       * the source with the destination, with the source taking precedence.
       * <p>
       * <strong>Note:</strong> This method tries to preserve the files' last
       * modified date/times using {@link File#setLastModified(long)}, however
       * it is not guaranteed that those operations will succeed.
       * If the modification operation fails, no indication is provided.
       *
       * <h4>Example: Copy directories only</h4> 
       *  <pre>
       *  // only copy the directory structure
       *  FileUtils.copyDirectory(srcDir, destDir, DirectoryFileFilter.DIRECTORY);
       *  </pre>
       *
       * <h4>Example: Copy directories and txt files</h4>
       *  <pre>
       *  // Create a filter for ".txt" files
       *  IOFileFilter txtSuffixFilter = FileFilterUtils.suffixFileFilter(".txt");
       *  IOFileFilter txtFiles = FileFilterUtils.andFileFilter(FileFileFilter.FILE, txtSuffixFilter);
       *
       *  // Create a filter for either directories or ".txt" files
       *  FileFilter filter = FileFilterUtils.orFileFilter(DirectoryFileFilter.DIRECTORY, txtFiles);
       *
       *  // Copy using the filter
       *  FileUtils.copyDirectory(srcDir, destDir, filter);
       *  </pre>
       *
       * @param srcDir  an existing directory to copy, must not be {@code null}
       * @param destDir  the new directory, must not be {@code null}
       * @param filter  the filter to apply, null means copy all directories and files
       *  should be the same as the original
       *
       * @throws NullPointerException if source or destination is {@code null}
       * @throws IOException if source or destination is invalid
       * @throws IOException if an IO error occurs during copying
       * @since 1.4
       */
      public static void copyDirectory(File srcDir, File destDir,
              FileFilter filter) throws IOException {
          copyDirectory(srcDir, destDir, filter, true);
      }
  
      /**
       * Copies a filtered directory to a new location.
       * <p>
       * This method copies the contents of the specified source directory
       * to within the specified destination directory.
       * <p>
       * The destination directory is created if it does not exist.
       * If the destination directory did exist, then this method merges
       * the source with the destination, with the source taking precedence.
       * <p>
       * <strong>Note:</strong> Setting <code>preserveFileDate</code> to
       * {@code true} tries to preserve the files' last modified
       * date/times using {@link File#setLastModified(long)}, however it is
       * not guaranteed that those operations will succeed.
       * If the modification operation fails, no indication is provided.
       *
       * <h4>Example: Copy directories only</h4> 
       *  <pre>
       *  // only copy the directory structure
       *  FileUtils.copyDirectory(srcDir, destDir, DirectoryFileFilter.DIRECTORY, false);
       *  </pre>
       *
       * <h4>Example: Copy directories and txt files</h4>
       *  <pre>
       *  // Create a filter for ".txt" files
       *  IOFileFilter txtSuffixFilter = FileFilterUtils.suffixFileFilter(".txt");
       *  IOFileFilter txtFiles = FileFilterUtils.andFileFilter(FileFileFilter.FILE, txtSuffixFilter);
       *
       *  // Create a filter for either directories or ".txt" files
       *  FileFilter filter = FileFilterUtils.orFileFilter(DirectoryFileFilter.DIRECTORY, txtFiles);
       *
       *  // Copy using the filter
       *  FileUtils.copyDirectory(srcDir, destDir, filter, false);
       *  </pre>
       * 
       * @param srcDir  an existing directory to copy, must not be {@code null}
       * @param destDir  the new directory, must not be {@code null}
       * @param filter  the filter to apply, null means copy all directories and files
       * @param preserveFileDate  true if the file date of the copy
       *  should be the same as the original
       *
       * @throws NullPointerException if source or destination is {@code null}
       * @throws IOException if source or destination is invalid
       * @throws IOException if an IO error occurs during copying
       * @since 1.4
       */
      public static void copyDirectory(File srcDir, File destDir,
              FileFilter filter, boolean preserveFileDate) throws IOException {
          if (srcDir == null) {
              throw new NullPointerException("Source must not be null");
          }
          if (destDir == null) {
              throw new NullPointerException("Destination must not be null");
          }
          if (srcDir.exists() == false) {
              throw new FileNotFoundException("Source '" + srcDir + "' does not exist");
          }
          if (srcDir.isDirectory() == false) {
              throw new IOException("Source '" + srcDir + "' exists but is not a directory");
          }
          if (srcDir.getCanonicalPath().equals(destDir.getCanonicalPath())) {
              throw new IOException("Source '" + srcDir + "' and destination '" + destDir + "' are the same");
          }
  
          // Cater for destination being directory within the source directory (see IO-141)
          List<String> exclusionList = null;
          if (destDir.getCanonicalPath().startsWith(srcDir.getCanonicalPath())) {
              File[] srcFiles = filter == null ? srcDir.listFiles() : srcDir.listFiles(filter);
              if (srcFiles != null && srcFiles.length > 0) {
                  exclusionList = new ArrayList<String>(srcFiles.length);
                  for (File srcFile : srcFiles) {
                      File copiedFile = new File(destDir, srcFile.getName());
                      exclusionList.add(copiedFile.getCanonicalPath());
                  }
              }
          }
          doCopyDirectory(srcDir, destDir, filter, preserveFileDate, exclusionList);
      }
  
      /**
       * Internal copy directory method.
       * 
       * @param srcDir  the validated source directory, must not be {@code null}
       * @param destDir  the validated destination directory, must not be {@code null}
       * @param filter  the filter to apply, null means copy all directories and files
       * @param preserveFileDate  whether to preserve the file date
       * @param exclusionList  List of files and directories to exclude from the copy, may be null
       * @throws IOException if an error occurs
       * @since 1.1
       */
      private static void doCopyDirectory(File srcDir, File destDir, FileFilter filter,
              boolean preserveFileDate, List<String> exclusionList) throws IOException {
          // recurse
          File[] srcFiles = filter == null ? srcDir.listFiles() : srcDir.listFiles(filter);
          if (srcFiles == null) {  // null if abstract pathname does not denote a directory, or if an I/O error occurs
              throw new IOException("Failed to list contents of " + srcDir);
          }
          if (destDir.exists()) {
              if (destDir.isDirectory() == false) {
                  throw new IOException("Destination '" + destDir + "' exists but is not a directory");
              }
          } else {
              if (!destDir.mkdirs() && !destDir.isDirectory()) {
                  throw new IOException("Destination '" + destDir + "' directory cannot be created");
              }
          }
          if (destDir.canWrite() == false) {
              throw new IOException("Destination '" + destDir + "' cannot be written to");
          }
          for (File srcFile : srcFiles) {
              File dstFile = new File(destDir, srcFile.getName());
              if (exclusionList == null || !exclusionList.contains(srcFile.getCanonicalPath())) {
                  if (srcFile.isDirectory()) {
                      doCopyDirectory(srcFile, dstFile, filter, preserveFileDate, exclusionList);
                  } else {
                      doCopyFile(srcFile, dstFile, preserveFileDate);
                  }
              }
          }
  
          // Do this last, as the above has probably affected directory metadata
          if (preserveFileDate) {
              destDir.setLastModified(srcDir.lastModified());
          }
      }
  
      //-----------------------------------------------------------------------
      /**
       * Copies bytes from the URL <code>source</code> to a file
       * <code>destination</code>. The directories up to <code>destination</code>
       * will be created if they don't already exist. <code>destination</code>
       * will be overwritten if it already exists.
       * <p>
       * Warning: this method does not set a connection or read timeout and thus
       * might block forever. Use {@link #copyURLToFile(URL, File, int, int)}
       * with reasonable timeouts to prevent this.
       *
       * @param source  the <code>URL</code> to copy bytes from, must not be {@code null}
       * @param destination  the non-directory <code>File</code> to write bytes to
       *  (possibly overwriting), must not be {@code null}
       * @throws IOException if <code>source</code> URL cannot be opened
       * @throws IOException if <code>destination</code> is a directory
       * @throws IOException if <code>destination</code> cannot be written
       * @throws IOException if <code>destination</code> needs creating but can't be
       * @throws IOException if an IO error occurs during copying
       */
      public static void copyURLToFile(URL source, File destination) throws IOException {
          InputStream input = source.openStream();
          copyInputStreamToFile(input, destination);
      }
  
      /**
       * Copies bytes from the URL <code>source</code> to a file
       * <code>destination</code>. The directories up to <code>destination</code>
       * will be created if they don't already exist. <code>destination</code>
       * will be overwritten if it already exists.
       *
       * @param source  the <code>URL</code> to copy bytes from, must not be {@code null}
       * @param destination  the non-directory <code>File</code> to write bytes to
       *  (possibly overwriting), must not be {@code null}
       * @param connectionTimeout the number of milliseconds until this method
       *  will timeout if no connection could be established to the <code>source</code>
       * @param readTimeout the number of milliseconds until this method will
       *  timeout if no data could be read from the <code>source</code> 
       * @throws IOException if <code>source</code> URL cannot be opened
       * @throws IOException if <code>destination</code> is a directory
       * @throws IOException if <code>destination</code> cannot be written
       * @throws IOException if <code>destination</code> needs creating but can't be
       * @throws IOException if an IO error occurs during copying
       * @since 2.0
       */
      public static void copyURLToFile(URL source, File destination,
              int connectionTimeout, int readTimeout) throws IOException {
          URLConnection connection = source.openConnection();
          connection.setConnectTimeout(connectionTimeout);
          connection.setReadTimeout(readTimeout);
          InputStream input = connection.getInputStream();
          copyInputStreamToFile(input, destination);
      }
  
      /**
       * Copies bytes from an {@link InputStream} <code>source</code> to a file
       * <code>destination</code>. The directories up to <code>destination</code>
       * will be created if they don't already exist. <code>destination</code>
       * will be overwritten if it already exists.
       *
       * @param source  the <code>InputStream</code> to copy bytes from, must not be {@code null}
       * @param destination  the non-directory <code>File</code> to write bytes to
       *  (possibly overwriting), must not be {@code null}
       * @throws IOException if <code>destination</code> is a directory
       * @throws IOException if <code>destination</code> cannot be written
       * @throws IOException if <code>destination</code> needs creating but can't be
       * @throws IOException if an IO error occurs during copying
       * @since 2.0
       */
      public static void copyInputStreamToFile(InputStream source, File destination) throws IOException {
          try {
              FileOutputStream output = openOutputStream(destination);
              try {
                  IOUtils.copy(source, output);
                  output.close(); // don't swallow close Exception if copy completes normally
              } finally {
                  IOUtils.closeQuietly(output);
              }
          } finally {
              IOUtils.closeQuietly(source);
          }
      }
  
      //-----------------------------------------------------------------------
      /**
       * Deletes a directory recursively. 
       *
       * @param directory  directory to delete
       * @throws IOException in case deletion is unsuccessful
       */
      public static void deleteDirectory(File directory) throws IOException {
          if (!directory.exists()) {
              return;
          }
  
          if (!isSymlink(directory)) {
              cleanDirectory(directory);
          }
  
          if (!directory.delete()) {
              String message =
                  "Unable to delete directory " + directory + ".";
              throw new IOException(message);
          }
      }
  
      /**
       * Deletes a file, never throwing an exception. If file is a directory, delete it and all sub-directories.
       * <p>
       * The difference between File.delete() and this method are:
       * <ul>
       * <li>A directory to be deleted does not have to be empty.</li>
       * <li>No exceptions are thrown when a file or directory cannot be deleted.</li>
       * </ul>
       *
       * @param file  file or directory to delete, can be {@code null}
       * @return {@code true} if the file or directory was deleted, otherwise
       * {@code false}
       *
       * @since 1.4
       */
      public static boolean deleteQuietly(File file) {
          if (file == null) {
              return false;
          }
          try {
              if (file.isDirectory()) {
                  cleanDirectory(file);
              }
          } catch (Exception ignored) {
          }
  
          try {
              return file.delete();
          } catch (Exception ignored) {
              return false;
          }
      }
  
      /**
       * Determines whether the {@code parent} directory contains the {@code child} element (a file or directory).
       * <p>
       * Files are normalized before comparison.
       * </p>
       * 
       * Edge cases:
       * <ul>
       * <li>A {@code directory} must not be null: if null, throw IllegalArgumentException</li>
       * <li>A {@code directory} must be a directory: if not a directory, throw IllegalArgumentException</li>
       * <li>A directory does not contain itself: return false</li>
       * <li>A null child file is not contained in any parent: return false</li>
       * </ul>
       * 
       * @param directory
       *            the file to consider as the parent.
       * @param child
       *            the file to consider as the child.
       * @return true is the candidate leaf is under by the specified composite. False otherwise.
       * @throws IOException
       *             if an IO error occurs while checking the files.
       * @since 2.2
       * @see FilenameUtils#directoryContains(String, String)
       */
      public static boolean directoryContains(final File directory, final File child) throws IOException {
          
          // Fail fast against NullPointerException
          if (directory == null) {
              throw new IllegalArgumentException("Directory must not be null");
          }
      
          if (!directory.isDirectory()) {
              throw new IllegalArgumentException("Not a directory: " + directory);
          }
      
          if (child == null) {
              return false;
          }
      
          if (!directory.exists() || !child.exists()) {
              return false;
          }
      
          // Canonicalize paths (normalizes relative paths)
          String canonicalParent = directory.getCanonicalPath();
          String canonicalChild = child.getCanonicalPath();
      
          return FilenameUtils.directoryContains(canonicalParent, canonicalChild);
      }
  
      /**
       * Cleans a directory without deleting it.
       *
       * @param directory directory to clean
       * @throws IOException in case cleaning is unsuccessful
       */
      public static void cleanDirectory(File directory) throws IOException {
          if (!directory.exists()) {
              String message = directory + " does not exist";
              throw new IllegalArgumentException(message);
          }
  
          if (!directory.isDirectory()) {
              String message = directory + " is not a directory";
              throw new IllegalArgumentException(message);
          }
  
          File[] files = directory.listFiles();
          if (files == null) {  // null if security restricted
              throw new IOException("Failed to list contents of " + directory);
          }
  
          IOException exception = null;
          for (File file : files) {
              try {
                  forceDelete(file);
              } catch (IOException ioe) {
                  exception = ioe;
              }
          }
  
          if (null != exception) {
              throw exception;
          }
      }
  
      //-----------------------------------------------------------------------
      /**
       * Waits for NFS to propagate a file creation, imposing a timeout.
       * <p>
       * This method repeatedly tests {@link File#exists()} until it returns
       * true up to the maximum time specified in seconds.
       *
       * @param file  the file to check, must not be {@code null}
       * @param seconds  the maximum time in seconds to wait
       * @return true if file exists
       * @throws NullPointerException if the file is {@code null}
       */
      public static boolean waitFor(File file, int seconds) {
          int timeout = 0;
          int tick = 0;
          while (!file.exists()) {
              if (tick++ >= 10) {
                  tick = 0;
                  if (timeout++ > seconds) {
                      return false;
                  }
              }
              try {
                  Thread.sleep(100);
              } catch (InterruptedException ignore) {
                  // ignore exception
              } catch (Exception ex) {
                  break;
              }
          }
          return true;
      }
  
      //-----------------------------------------------------------------------
      /**
       * Reads the contents of a file into a String.
       * The file is always closed.
       *
       * @param file  the file to read, must not be {@code null}
       * @param encoding  the encoding to use, {@code null} means platform default
       * @return the file contents, never {@code null}
       * @throws IOException in case of an I/O error
       * @since 2.3
       */
      public static String readFileToString(File file, Charset encoding) throws IOException {
          InputStream in = null;
          try {
              in = openInputStream(file);
              return IOUtils.toString(in, Charsets.toCharset(encoding));
          } finally {
              IOUtils.closeQuietly(in);
          }
      }
  
      /**
       * Reads the contents of a file into a String. The file is always closed.
       * 
       * @param file
       *            the file to read, must not be {@code null}
       * @param encoding
       *            the encoding to use, {@code null} means platform default
       * @return the file contents, never {@code null}
       * @throws IOException
       *             in case of an I/O error
       * @throws UnsupportedCharsetException
       *             thrown instead of {@link UnsupportedEncodingException} in version 2.2 if the encoding is not
       *             supported.
       * @since 2.3
       */
      public static String readFileToString(File file, String encoding) throws IOException {
          return readFileToString(file, Charsets.toCharset(encoding));
      }
  
  
      /**
       * Reads the contents of a file into a String using the default encoding for the VM. 
       * The file is always closed.
       *
       * @param file  the file to read, must not be {@code null}
       * @return the file contents, never {@code null}
       * @throws IOException in case of an I/O error
       * @since 1.3.1
       */
      public static String readFileToString(File file) throws IOException {
          return readFileToString(file, Charset.defaultCharset());
      }
  
      /**
       * Reads the contents of a file into a byte array.
       * The file is always closed.
       *
       * @param file  the file to read, must not be {@code null}
       * @return the file contents, never {@code null}
       * @throws IOException in case of an I/O error
       * @since 1.1
       */
      public static byte[] readFileToByteArray(File file) throws IOException {
          InputStream in = null;
          try {
              in = openInputStream(file);
              return IOUtils.toByteArray(in, file.length());
          } finally {
              IOUtils.closeQuietly(in);
          }
      }
  
      /**
       * Reads the contents of a file line by line to a List of Strings.
       * The file is always closed.
       *
       * @param file  the file to read, must not be {@code null}
       * @param encoding  the encoding to use, {@code null} means platform default
       * @return the list of Strings representing each line in the file, never {@code null}
       * @throws IOException in case of an I/O error
       * @since 2.3
       */
      public static List<String> readLines(File file, Charset encoding) throws IOException {
          InputStream in = null;
          try {
              in = openInputStream(file);
              return IOUtils.readLines(in, Charsets.toCharset(encoding));
          } finally {
              IOUtils.closeQuietly(in);
          }
      }
  
      /**
       * Reads the contents of a file line by line to a List of Strings. The file is always closed.
       * 
       * @param file
       *            the file to read, must not be {@code null}
       * @param encoding
       *            the encoding to use, {@code null} means platform default
       * @return the list of Strings representing each line in the file, never {@code null}
       * @throws IOException
       *             in case of an I/O error
       * @throws UnsupportedCharsetException
       *             thrown instead of {@link UnsupportedEncodingException} in version 2.2 if the encoding is not
       *             supported.
       * @since 1.1
       */
      public static List<String> readLines(File file, String encoding) throws IOException {
          return readLines(file, Charsets.toCharset(encoding));
      }
  
      /**
       * Reads the contents of a file line by line to a List of Strings using the default encoding for the VM.
       * The file is always closed.
       *
       * @param file  the file to read, must not be {@code null}
       * @return the list of Strings representing each line in the file, never {@code null}
       * @throws IOException in case of an I/O error
       * @since 1.3
       */
      public static List<String> readLines(File file) throws IOException {
          return readLines(file, Charset.defaultCharset());
      }
  
      /**
       * Returns an Iterator for the lines in a <code>File</code>.
       * <p>
       * This method opens an <code>InputStream</code> for the file.
       * When you have finished with the iterator you should close the stream
       * to free internal resources. This can be done by calling the
       * {@link LineIterator#close()} or
       * {@link LineIterator#closeQuietly(LineIterator)} method.
       * <p>
       * The recommended usage pattern is:
       * <pre>
       * LineIterator it = FileUtils.lineIterator(file, "UTF-8");
       * try {
       *   while (it.hasNext()) {
       *     String line = it.nextLine();
       *     /// do something with line
       *   }
       * } finally {
       *   LineIterator.closeQuietly(iterator);
       * }
       * </pre>
       * <p>
       * If an exception occurs during the creation of the iterator, the
       * underlying stream is closed.
       *
       * @param file  the file to open for input, must not be {@code null}
       * @param encoding  the encoding to use, {@code null} means platform default
       * @return an Iterator of the lines in the file, never {@code null}
       * @throws IOException in case of an I/O error (file closed)
       * @since 1.2
       */
      public static LineIterator lineIterator(File file, String encoding) throws IOException {
          InputStream in = null;
          try {
              in = openInputStream(file);
              return IOUtils.lineIterator(in, encoding);
          } catch (IOException ex) {
              IOUtils.closeQuietly(in);
              throw ex;
          } catch (RuntimeException ex) {
              IOUtils.closeQuietly(in);
              throw ex;
          }
      }
  
      /**
       * Returns an Iterator for the lines in a <code>File</code> using the default encoding for the VM.
       *
       * @param file  the file to open for input, must not be {@code null}
       * @return an Iterator of the lines in the file, never {@code null}
       * @throws IOException in case of an I/O error (file closed)
       * @since 1.3
       * @see #lineIterator(File, String)
       */
      public static LineIterator lineIterator(File file) throws IOException {
          return lineIterator(file, null);
      }
  
      //-----------------------------------------------------------------------
      /**
       * Writes a String to a file creating the file if it does not exist.
       *
       * NOTE: As from v1.3, the parent directories of the file will be created
       * if they do not exist.
       *
       * @param file  the file to write
       * @param data  the content to write to the file
       * @param encoding  the encoding to use, {@code null} means platform default
       * @throws IOException in case of an I/O error
       * @throws java.io.UnsupportedEncodingException if the encoding is not supported by the VM
       * @since 2.4
       */
      public static void writeStringToFile(File file, String data, Charset encoding) throws IOException {
          writeStringToFile(file, data, encoding, false);
      }
  
      /**
       * Writes a String to a file creating the file if it does not exist.
       *
       * NOTE: As from v1.3, the parent directories of the file will be created
       * if they do not exist.
       *
       * @param file  the file to write
       * @param data  the content to write to the file
       * @param encoding  the encoding to use, {@code null} means platform default
       * @throws IOException in case of an I/O error
       * @throws java.io.UnsupportedEncodingException if the encoding is not supported by the VM
       */
      public static void writeStringToFile(File file, String data, String encoding) throws IOException {
          writeStringToFile(file, data, encoding, false);
      }
  
      /**
       * Writes a String to a file creating the file if it does not exist.
       *
       * @param file  the file to write
       * @param data  the content to write to the file
       * @param encoding  the encoding to use, {@code null} means platform default
       * @param append if {@code true}, then the String will be added to the
       * end of the file rather than overwriting
       * @throws IOException in case of an I/O error
       * @since 2.3
       */
      public static void writeStringToFile(File file, String data, Charset encoding, boolean append) throws IOException {
          OutputStream out = null;
          try {
              out = openOutputStream(file, append);
              IOUtils.write(data, out, encoding);
              out.close(); // don't swallow close Exception if copy completes normally
          } finally {
              IOUtils.closeQuietly(out);
          }
      }
  
      /**
       * Writes a String to a file creating the file if it does not exist.
       *
       * @param file  the file to write
       * @param data  the content to write to the file
       * @param encoding  the encoding to use, {@code null} means platform default
       * @param append if {@code true}, then the String will be added to the
       * end of the file rather than overwriting
       * @throws IOException in case of an I/O error
       * @throws UnsupportedCharsetException
       *             thrown instead of {@link UnsupportedEncodingException} in version 2.2 if the encoding is not
       *             supported by the VM
       * @since 2.1
       */
      public static void writeStringToFile(File file, String data, String encoding, boolean append) throws IOException {
          writeStringToFile(file, data, Charsets.toCharset(encoding), append);
      }
  
      /**
       * Writes a String to a file creating the file if it does not exist using the default encoding for the VM.
       * 
       * @param file  the file to write
       * @param data  the content to write to the file
       * @throws IOException in case of an I/O error
       */
      public static void writeStringToFile(File file, String data) throws IOException {
          writeStringToFile(file, data, Charset.defaultCharset(), false);
      }
  
      /**
       * Writes a String to a file creating the file if it does not exist using the default encoding for the VM.
       * 
       * @param file  the file to write
       * @param data  the content to write to the file
       * @param append if {@code true}, then the String will be added to the
       * end of the file rather than overwriting
       * @throws IOException in case of an I/O error
       * @since 2.1
       */
      public static void writeStringToFile(File file, String data, boolean append) throws IOException {
          writeStringToFile(file, data, Charset.defaultCharset(), append);
      }
  
      /**
       * Writes a CharSequence to a file creating the file if it does not exist using the default encoding for the VM.
       * 
       * @param file  the file to write
       * @param data  the content to write to the file
       * @throws IOException in case of an I/O error
       * @since 2.0
       */
      public static void write(File file, CharSequence data) throws IOException {
          write(file, data, Charset.defaultCharset(), false);
      }
  
      /**
       * Writes a CharSequence to a file creating the file if it does not exist using the default encoding for the VM.
       * 
       * @param file  the file to write
       * @param data  the content to write to the file
       * @param append if {@code true}, then the data will be added to the
       * end of the file rather than overwriting
       * @throws IOException in case of an I/O error
       * @since 2.1
       */
      public static void write(File file, CharSequence data, boolean append) throws IOException {
          write(file, data, Charset.defaultCharset(), append);
      }
  
      /**
       * Writes a CharSequence to a file creating the file if it does not exist.
       *
       * @param file  the file to write
       * @param data  the content to write to the file
       * @param encoding  the encoding to use, {@code null} means platform default
       * @throws IOException in case of an I/O error
       * @since 2.3
       */
      public static void write(File file, CharSequence data, Charset encoding) throws IOException {
          write(file, data, encoding, false);
      }
  
      /**
       * Writes a CharSequence to a file creating the file if it does not exist.
       *
       * @param file  the file to write
       * @param data  the content to write to the file
       * @param encoding  the encoding to use, {@code null} means platform default
       * @throws IOException in case of an I/O error
       * @throws java.io.UnsupportedEncodingException if the encoding is not supported by the VM
       * @since 2.0
       */
      public static void write(File file, CharSequence data, String encoding) throws IOException {
          write(file, data, encoding, false);
      }
  
      /**
       * Writes a CharSequence to a file creating the file if it does not exist.
       *
       * @param file  the file to write
       * @param data  the content to write to the file
       * @param encoding  the encoding to use, {@code null} means platform default
       * @param append if {@code true}, then the data will be added to the
       * end of the file rather than overwriting
       * @throws IOException in case of an I/O error
       * @since 2.3
       */
      public static void write(File file, CharSequence data, Charset encoding, boolean append) throws IOException {
          String str = data == null ? null : data.toString();
          writeStringToFile(file, str, encoding, append);
      }
  
      /**
       * Writes a CharSequence to a file creating the file if it does not exist.
       *
       * @param file  the file to write
       * @param data  the content to write to the file
       * @param encoding  the encoding to use, {@code null} means platform default
       * @param append if {@code true}, then the data will be added to the
       * end of the file rather than overwriting
       * @throws IOException in case of an I/O error
       * @throws UnsupportedCharsetException
       *             thrown instead of {@link UnsupportedEncodingException} in version 2.2 if the encoding is not
       *             supported by the VM
       * @since IO 2.1
       */
      public static void write(File file, CharSequence data, String encoding, boolean append) throws IOException {
          write(file, data, Charsets.toCharset(encoding), append);
      }
  
      /**
       * Writes a byte array to a file creating the file if it does not exist.
       * <p>
       * NOTE: As from v1.3, the parent directories of the file will be created
       * if they do not exist.
       *
       * @param file  the file to write to
       * @param data  the content to write to the file
       * @throws IOException in case of an I/O error
       * @since 1.1
       */
      public static void writeByteArrayToFile(File file, byte[] data) throws IOException {
          writeByteArrayToFile(file, data, false);
      }
  
      /**
       * Writes a byte array to a file creating the file if it does not exist.
       *
       * @param file  the file to write to
       * @param data  the content to write to the file
       * @param append if {@code true}, then bytes will be added to the
       * end of the file rather than overwriting
       * @throws IOException in case of an I/O error
       * @since IO 2.1
       */
      public static void writeByteArrayToFile(File file, byte[] data, boolean append) throws IOException {
          OutputStream out = null;
          try {
              out = openOutputStream(file, append);
              out.write(data);
              out.close(); // don't swallow close Exception if copy completes normally
          } finally {
              IOUtils.closeQuietly(out);
          }
      }
  
      /**
       * Writes the <code>toString()</code> value of each item in a collection to
       * the specified <code>File</code> line by line.
       * The specified character encoding and the default line ending will be used.
       * <p>
       * NOTE: As from v1.3, the parent directories of the file will be created
       * if they do not exist.
       *
       * @param file  the file to write to
       * @param encoding  the encoding to use, {@code null} means platform default
       * @param lines  the lines to write, {@code null} entries produce blank lines
       * @throws IOException in case of an I/O error
       * @throws java.io.UnsupportedEncodingException if the encoding is not supported by the VM
       * @since 1.1
       */
      public static void writeLines(File file, String encoding, Collection<?> lines) throws IOException {
          writeLines(file, encoding, lines, null, false);
      }
  
      /**
       * Writes the <code>toString()</code> value of each item in a collection to
       * the specified <code>File</code> line by line, optionally appending.
       * The specified character encoding and the default line ending will be used.
       *
       * @param file  the file to write to
       * @param encoding  the encoding to use, {@code null} means platform default
       * @param lines  the lines to write, {@code null} entries produce blank lines
       * @param append if {@code true}, then the lines will be added to the
       * end of the file rather than overwriting
       * @throws IOException in case of an I/O error
       * @throws java.io.UnsupportedEncodingException if the encoding is not supported by the VM
       * @since 2.1
       */
      public static void writeLines(File file, String encoding, Collection<?> lines, boolean append) throws IOException {
          writeLines(file, encoding, lines, null, append);
      }
  
      /**
       * Writes the <code>toString()</code> value of each item in a collection to
       * the specified <code>File</code> line by line.
       * The default VM encoding and the default line ending will be used.
       *
       * @param file  the file to write to
       * @param lines  the lines to write, {@code null} entries produce blank lines
       * @throws IOException in case of an I/O error
       * @since 1.3
       */
      public static void writeLines(File file, Collection<?> lines) throws IOException {
          writeLines(file, null, lines, null, false);
      }
      
      /**
       * Writes the <code>toString()</code> value of each item in a collection to
       * the specified <code>File</code> line by line.
       * The default VM encoding and the default line ending will be used.
       *
       * @param file  the file to write to
       * @param lines  the lines to write, {@code null} entries produce blank lines
       * @param append if {@code true}, then the lines will be added to the
       * end of the file rather than overwriting
       * @throws IOException in case of an I/O error
       * @since 2.1
       */
      public static void writeLines(File file, Collection<?> lines, boolean append) throws IOException {
          writeLines(file, null, lines, null, append);
      }
  
      /**
       * Writes the <code>toString()</code> value of each item in a collection to
       * the specified <code>File</code> line by line.
       * The specified character encoding and the line ending will be used.
       * <p>
       * NOTE: As from v1.3, the parent directories of the file will be created
       * if they do not exist.
       *
       * @param file  the file to write to
       * @param encoding  the encoding to use, {@code null} means platform default
       * @param lines  the lines to write, {@code null} entries produce blank lines
       * @param lineEnding  the line separator to use, {@code null} is system default
       * @throws IOException in case of an I/O error
       * @throws java.io.UnsupportedEncodingException if the encoding is not supported by the VM
       * @since 1.1
       */
      public static void writeLines(File file, String encoding, Collection<?> lines, String lineEnding)
          throws IOException {
          writeLines(file, encoding, lines, lineEnding, false);
      }
  
      /**
       * Writes the <code>toString()</code> value of each item in a collection to
       * the specified <code>File</code> line by line.
       * The specified character encoding and the line ending will be used.
       *
       * @param file  the file to write to
       * @param encoding  the encoding to use, {@code null} means platform default
       * @param lines  the lines to write, {@code null} entries produce blank lines
       * @param lineEnding  the line separator to use, {@code null} is system default
       * @param append if {@code true}, then the lines will be added to the
       * end of the file rather than overwriting
       * @throws IOException in case of an I/O error
       * @throws java.io.UnsupportedEncodingException if the encoding is not supported by the VM
       * @since 2.1
       */
      public static void writeLines(File file, String encoding, Collection<?> lines, String lineEnding, boolean append)
              throws IOException {
          FileOutputStream out = null;
          try {
              out = openOutputStream(file, append);
              final BufferedOutputStream buffer = new BufferedOutputStream(out);
              IOUtils.writeLines(lines, lineEnding, buffer, encoding);
              buffer.flush();
              out.close(); // don't swallow close Exception if copy completes normally
          } finally {
              IOUtils.closeQuietly(out);
          }
      }
  
      /**
       * Writes the <code>toString()</code> value of each item in a collection to
       * the specified <code>File</code> line by line.
       * The default VM encoding and the specified line ending will be used.
       *
       * @param file  the file to write to
       * @param lines  the lines to write, {@code null} entries produce blank lines
       * @param lineEnding  the line separator to use, {@code null} is system default
       * @throws IOException in case of an I/O error
       * @since 1.3
       */
      public static void writeLines(File file, Collection<?> lines, String lineEnding) throws IOException {
          writeLines(file, null, lines, lineEnding, false);
      }
  
      /**
       * Writes the <code>toString()</code> value of each item in a collection to
       * the specified <code>File</code> line by line.
       * The default VM encoding and the specified line ending will be used.
       *
       * @param file  the file to write to
       * @param lines  the lines to write, {@code null} entries produce blank lines
       * @param lineEnding  the line separator to use, {@code null} is system default
       * @param append if {@code true}, then the lines will be added to the
       * end of the file rather than overwriting
       * @throws IOException in case of an I/O error
       * @since 2.1
       */
      public static void writeLines(File file, Collection<?> lines, String lineEnding, boolean append)
          throws IOException {
          writeLines(file, null, lines, lineEnding, append);
      }
  
      //-----------------------------------------------------------------------
      /**
       * Deletes a file. If file is a directory, delete it and all sub-directories.
       * <p>
       * The difference between File.delete() and this method are:
       * <ul>
       * <li>A directory to be deleted does not have to be empty.</li>
       * <li>You get exceptions when a file or directory cannot be deleted.
       *      (java.io.File methods returns a boolean)</li>
       * </ul>
       *
       * @param file  file or directory to delete, must not be {@code null}
       * @throws NullPointerException if the directory is {@code null}
       * @throws FileNotFoundException if the file was not found
       * @throws IOException in case deletion is unsuccessful
       */
      public static void forceDelete(File file) throws IOException {
          if (file.isDirectory()) {
              deleteDirectory(file);
          } else {
              boolean filePresent = file.exists();
              if (!file.delete()) {
                  if (!filePresent){
                      throw new FileNotFoundException("File does not exist: " + file);
                  }
                  String message =
                      "Unable to delete file: " + file;
                  throw new IOException(message);
              }
          }
      }
  
      /**
       * Schedules a file to be deleted when JVM exits.
       * If file is directory delete it and all sub-directories.
       *
       * @param file  file or directory to delete, must not be {@code null}
       * @throws NullPointerException if the file is {@code null}
       * @throws IOException in case deletion is unsuccessful
       */
      public static void forceDeleteOnExit(File file) throws IOException {
          if (file.isDirectory()) {
              deleteDirectoryOnExit(file);
          } else {
              file.deleteOnExit();
          }
      }
  
      /**
       * Schedules a directory recursively for deletion on JVM exit.
       *
       * @param directory  directory to delete, must not be {@code null}
       * @throws NullPointerException if the directory is {@code null}
       * @throws IOException in case deletion is unsuccessful
       */
      private static void deleteDirectoryOnExit(File directory) throws IOException {
          if (!directory.exists()) {
              return;
          }
  
          directory.deleteOnExit();
          if (!isSymlink(directory)) {
              cleanDirectoryOnExit(directory);
          }
      }
  
      /**
       * Cleans a directory without deleting it.
       *
       * @param directory  directory to clean, must not be {@code null}
       * @throws NullPointerException if the directory is {@code null}
       * @throws IOException in case cleaning is unsuccessful
       */
      private static void cleanDirectoryOnExit(File directory) throws IOException {
          if (!directory.exists()) {
              String message = directory + " does not exist";
              throw new IllegalArgumentException(message);
          }
  
          if (!directory.isDirectory()) {
              String message = directory + " is not a directory";
              throw new IllegalArgumentException(message);
          }
  
          File[] files = directory.listFiles();
          if (files == null) {  // null if security restricted
              throw new IOException("Failed to list contents of " + directory);
          }
  
          IOException exception = null;
          for (File file : files) {
              try {
                  forceDeleteOnExit(file);
              } catch (IOException ioe) {
                  exception = ioe;
              }
          }
  
          if (null != exception) {
              throw exception;
          }
      }
  
      /**
       * Makes a directory, including any necessary but nonexistent parent
       * directories. If a file already exists with specified name but it is
       * not a directory then an IOException is thrown.
       * If the directory cannot be created (or does not already exist)
       * then an IOException is thrown.
       *
       * @param directory  directory to create, must not be {@code null}
       * @throws NullPointerException if the directory is {@code null}
       * @throws IOException if the directory cannot be created or the file already exists but is not a directory
       */
      public static void forceMkdir(File directory) throws IOException {
          if (directory.exists()) {
              if (!directory.isDirectory()) {
                  String message =
                      "File "
                          + directory
                          + " exists and is "
                          + "not a directory. Unable to create directory.";
                  throw new IOException(message);
              }
          } else {
              if (!directory.mkdirs()) {
                  // Double-check that some other thread or process hasn't made
                  // the directory in the background
                  if (!directory.isDirectory())
                  {
                      String message =
                          "Unable to create directory " + directory;
                      throw new IOException(message);
                  }
              }
          }
      }
  
      //-----------------------------------------------------------------------
      /**
       * Returns the size of the specified file or directory. If the provided 
       * {@link File} is a regular file, then the file's length is returned.
       * If the argument is a directory, then the size of the directory is
       * calculated recursively. If a directory or subdirectory is security 
       * restricted, its size will not be included.
       * 
       * @param file the regular file or directory to return the size 
       *        of (must not be {@code null}).
       * 
       * @return the length of the file, or recursive size of the directory, 
       *         provided (in bytes).
       * 
       * @throws NullPointerException if the file is {@code null}
       * @throws IllegalArgumentException if the file does not exist.
       *         
       * @since 2.0
       */
      public static long sizeOf(File file) {
  
          if (!file.exists()) {
              String message = file + " does not exist";
              throw new IllegalArgumentException(message);
          }
  
          if (file.isDirectory()) {
              return sizeOfDirectory(file);
          } else {
              return file.length();
          }
  
      }
  
      /**
       * Returns the size of the specified file or directory. If the provided 
       * {@link File} is a regular file, then the file's length is returned.
       * If the argument is a directory, then the size of the directory is
       * calculated recursively. If a directory or subdirectory is security 
       * restricted, its size will not be included.
       * 
       * @param file the regular file or directory to return the size 
       *        of (must not be {@code null}).
       * 
       * @return the length of the file, or recursive size of the directory, 
       *         provided (in bytes).
       * 
       * @throws NullPointerException if the file is {@code null}
       * @throws IllegalArgumentException if the file does not exist.
       *         
       * @since 2.4
       */
      public static BigInteger sizeOfAsBigInteger(File file) {
  
          if (!file.exists()) {
              String message = file + " does not exist";
              throw new IllegalArgumentException(message);
          }
  
          if (file.isDirectory()) {
              return sizeOfDirectoryAsBigInteger(file);
          } else {
              return BigInteger.valueOf(file.length());
          }
  
      }
  
      /**
       * Counts the size of a directory recursively (sum of the length of all files).
       * 
       * @param directory
       *            directory to inspect, must not be {@code null}
       * @return size of directory in bytes, 0 if directory is security restricted, a negative number when the real total
       *         is greater than {@link Long#MAX_VALUE}.
       * @throws NullPointerException
       *             if the directory is {@code null}
       */
      public static long sizeOfDirectory(File directory) {
          checkDirectory(directory);
  
          final File[] files = directory.listFiles();
          if (files == null) {  // null if security restricted
              return 0L;
          }
          long size = 0;
  
          for (final File file : files) {
              try {
                  if (!isSymlink(file)) {
                      size += sizeOf(file);
                      if (size < 0) {
                          break;
                      }
                  }
              } catch (IOException ioe) {
                  // Ignore exceptions caught when asking if a File is a symlink.
              }
          }
  
          return size;
      }
  
      /**
       * Counts the size of a directory recursively (sum of the length of all files).
       * 
       * @param directory
       *            directory to inspect, must not be {@code null}
       * @return size of directory in bytes, 0 if directory is security restricted.
       * @throws NullPointerException
       *             if the directory is {@code null}
       *  @since 2.4
       */
      public static BigInteger sizeOfDirectoryAsBigInteger(File directory) {
          checkDirectory(directory);
  
          final File[] files = directory.listFiles();
          if (files == null) {  // null if security restricted
              return BigInteger.ZERO;
          }
          BigInteger size = BigInteger.ZERO;
  
          for (final File file : files) {
              try {
                  if (!isSymlink(file)) {
                      size = size.add(BigInteger.valueOf(sizeOf(file)));
                  }
              } catch (IOException ioe) {
                  // Ignore exceptions caught when asking if a File is a symlink.
              }
          }
  
          return size;
      }
  
      /**
       * Checks that the given {@code File} exists and is a directory.
       * 
       * @param directory The {@code File} to check.
       * @throws IllegalArgumentException if the given {@code File} does not exist or is not a directory.
       */
      private static void checkDirectory(File directory) {
          if (!directory.exists()) {
              throw new IllegalArgumentException(directory + " does not exist");
          }
          if (!directory.isDirectory()) {
              throw new IllegalArgumentException(directory + " is not a directory");
          }
      }
  
      //-----------------------------------------------------------------------
      /**
       * Tests if the specified <code>File</code> is newer than the reference
       * <code>File</code>.
       *
       * @param file  the <code>File</code> of which the modification date must
       * be compared, must not be {@code null}
       * @param reference  the <code>File</code> of which the modification date
       * is used, must not be {@code null}
       * @return true if the <code>File</code> exists and has been modified more
       * recently than the reference <code>File</code>
       * @throws IllegalArgumentException if the file is {@code null}
       * @throws IllegalArgumentException if the reference file is {@code null} or doesn't exist
       */
       public static boolean isFileNewer(File file, File reference) {
          if (reference == null) {
              throw new IllegalArgumentException("No specified reference file");
          }
          if (!reference.exists()) {
              throw new IllegalArgumentException("The reference file '"
                      + reference + "' doesn't exist");
          }
          return isFileNewer(file, reference.lastModified());
      }
  
      /**
       * Tests if the specified <code>File</code> is newer than the specified
       * <code>Date</code>.
       * 
       * @param file  the <code>File</code> of which the modification date
       * must be compared, must not be {@code null}
       * @param date  the date reference, must not be {@code null}
       * @return true if the <code>File</code> exists and has been modified
       * after the given <code>Date</code>.
       * @throws IllegalArgumentException if the file is {@code null}
       * @throws IllegalArgumentException if the date is {@code null}
       */
      public static boolean isFileNewer(File file, Date date) {
          if (date == null) {
              throw new IllegalArgumentException("No specified date");
          }
          return isFileNewer(file, date.getTime());
      }
  
      /**
       * Tests if the specified <code>File</code> is newer than the specified
       * time reference.
       *
       * @param file  the <code>File</code> of which the modification date must
       * be compared, must not be {@code null}
       * @param timeMillis  the time reference measured in milliseconds since the
       * epoch (00:00:00 GMT, January 1, 1970)
       * @return true if the <code>File</code> exists and has been modified after
       * the given time reference.
       * @throws IllegalArgumentException if the file is {@code null}
       */
       public static boolean isFileNewer(File file, long timeMillis) {
          if (file == null) {
              throw new IllegalArgumentException("No specified file");
          }
          if (!file.exists()) {
              return false;
          }
          return file.lastModified() > timeMillis;
      }
  
  
      //-----------------------------------------------------------------------
      /**
       * Tests if the specified <code>File</code> is older than the reference
       * <code>File</code>.
       *
       * @param file  the <code>File</code> of which the modification date must
       * be compared, must not be {@code null}
       * @param reference  the <code>File</code> of which the modification date
       * is used, must not be {@code null}
       * @return true if the <code>File</code> exists and has been modified before
       * the reference <code>File</code>
       * @throws IllegalArgumentException if the file is {@code null}
       * @throws IllegalArgumentException if the reference file is {@code null} or doesn't exist
       */
       public static boolean isFileOlder(File file, File reference) {
          if (reference == null) {
              throw new IllegalArgumentException("No specified reference file");
          }
          if (!reference.exists()) {
              throw new IllegalArgumentException("The reference file '"
                      + reference + "' doesn't exist");
          }
          return isFileOlder(file, reference.lastModified());
      }
  
      /**
       * Tests if the specified <code>File</code> is older than the specified
       * <code>Date</code>.
       * 
       * @param file  the <code>File</code> of which the modification date
       * must be compared, must not be {@code null}
       * @param date  the date reference, must not be {@code null}
       * @return true if the <code>File</code> exists and has been modified
       * before the given <code>Date</code>.
       * @throws IllegalArgumentException if the file is {@code null}
       * @throws IllegalArgumentException if the date is {@code null}
       */
      public static boolean isFileOlder(File file, Date date) {
          if (date == null) {
              throw new IllegalArgumentException("No specified date");
          }
          return isFileOlder(file, date.getTime());
      }
  
      /**
       * Tests if the specified <code>File</code> is older than the specified
       * time reference.
       *
       * @param file  the <code>File</code> of which the modification date must
       * be compared, must not be {@code null}
       * @param timeMillis  the time reference measured in milliseconds since the
       * epoch (00:00:00 GMT, January 1, 1970)
       * @return true if the <code>File</code> exists and has been modified before
       * the given time reference.
       * @throws IllegalArgumentException if the file is {@code null}
       */
       public static boolean isFileOlder(File file, long timeMillis) {
          if (file == null) {
              throw new IllegalArgumentException("No specified file");
          }
          if (!file.exists()) {
              return false;
          }
          return file.lastModified() < timeMillis;
      }
  
      //-----------------------------------------------------------------------
      /**
       * Computes the checksum of a file using the CRC32 checksum routine.
       * The value of the checksum is returned.
       *
       * @param file  the file to checksum, must not be {@code null}
       * @return the checksum value
       * @throws NullPointerException if the file or checksum is {@code null}
       * @throws IllegalArgumentException if the file is a directory
       * @throws IOException if an IO error occurs reading the file
       * @since 1.3
       */
      public static long checksumCRC32(File file) throws IOException {
          CRC32 crc = new CRC32();
          checksum(file, crc);
          return crc.getValue();
      }
  
      /**
       * Computes the checksum of a file using the specified checksum object.
       * Multiple files may be checked using one <code>Checksum</code> instance
       * if desired simply by reusing the same checksum object.
       * For example:
       * <pre>
       *   long csum = FileUtils.checksum(file, new CRC32()).getValue();
       * </pre>
       *
       * @param file  the file to checksum, must not be {@code null}
       * @param checksum  the checksum object to be used, must not be {@code null}
       * @return the checksum specified, updated with the content of the file
       * @throws NullPointerException if the file or checksum is {@code null}
       * @throws IllegalArgumentException if the file is a directory
       * @throws IOException if an IO error occurs reading the file
       * @since 1.3
       */
      public static Checksum checksum(File file, Checksum checksum) throws IOException {
          if (file.isDirectory()) {
              throw new IllegalArgumentException("Checksums can't be computed on directories");
          }
          InputStream in = null;
          try {
              in = new CheckedInputStream(new FileInputStream(file), checksum);
              IOUtils.copy(in, new NullOutputStream());
          } finally {
              IOUtils.closeQuietly(in);
          }
          return checksum;
      }
  
      /**
       * Moves a directory.
       * <p>
       * When the destination directory is on another file system, do a "copy and delete".
       *
       * @param srcDir the directory to be moved
       * @param destDir the destination directory
       * @throws NullPointerException if source or destination is {@code null}
       * @throws FileExistsException if the destination directory exists
       * @throws IOException if source or destination is invalid
       * @throws IOException if an IO error occurs moving the file
       * @since 1.4
       */
      public static void moveDirectory(File srcDir, File destDir) throws IOException {
          if (srcDir == null) {
              throw new NullPointerException("Source must not be null");
          }
          if (destDir == null) {
              throw new NullPointerException("Destination must not be null");
          }
          if (!srcDir.exists()) {
              throw new FileNotFoundException("Source '" + srcDir + "' does not exist");
          }
          if (!srcDir.isDirectory()) {
              throw new IOException("Source '" + srcDir + "' is not a directory");
          }
          if (destDir.exists()) {
              throw new FileExistsException("Destination '" + destDir + "' already exists");
          }
          boolean rename = srcDir.renameTo(destDir);
          if (!rename) {
              if (destDir.getCanonicalPath().startsWith(srcDir.getCanonicalPath())) {
                  throw new IOException("Cannot move directory: "+srcDir+" to a subdirectory of itself: "+destDir);
              }
              copyDirectory( srcDir, destDir );
              deleteDirectory( srcDir );
              if (srcDir.exists()) {
                  throw new IOException("Failed to delete original directory '" + srcDir +
                          "' after copy to '" + destDir + "'");
              }
          }
      }
  
      /**
       * Moves a directory to another directory.
       *
       * @param src the file to be moved
       * @param destDir the destination file
       * @param createDestDir If {@code true} create the destination directory,
       * otherwise if {@code false} throw an IOException
       * @throws NullPointerException if source or destination is {@code null}
       * @throws FileExistsException if the directory exists in the destination directory
       * @throws IOException if source or destination is invalid
       * @throws IOException if an IO error occurs moving the file
       * @since 1.4
       */
      public static void moveDirectoryToDirectory(File src, File destDir, boolean createDestDir) throws IOException {
          if (src == null) {
              throw new NullPointerException("Source must not be null");
          }
          if (destDir == null) {
              throw new NullPointerException("Destination directory must not be null");
          }
          if (!destDir.exists() && createDestDir) {
              destDir.mkdirs();
          }
          if (!destDir.exists()) {
              throw new FileNotFoundException("Destination directory '" + destDir +
                      "' does not exist [createDestDir=" + createDestDir +"]");
          }
          if (!destDir.isDirectory()) {
              throw new IOException("Destination '" + destDir + "' is not a directory");
          }
          moveDirectory(src, new File(destDir, src.getName()));
      
      }
  
      /**
       * Moves a file.
       * <p>
       * When the destination file is on another file system, do a "copy and delete".
       *
       * @param srcFile the file to be moved
       * @param destFile the destination file
       * @throws NullPointerException if source or destination is {@code null}
       * @throws FileExistsException if the destination file exists
       * @throws IOException if source or destination is invalid
       * @throws IOException if an IO error occurs moving the file
       * @since 1.4
       */
      public static void moveFile(File srcFile, File destFile) throws IOException {
          if (srcFile == null) {
              throw new NullPointerException("Source must not be null");
          }
          if (destFile == null) {
              throw new NullPointerException("Destination must not be null");
          }
          if (!srcFile.exists()) {
              throw new FileNotFoundException("Source '" + srcFile + "' does not exist");
          }
          if (srcFile.isDirectory()) {
              throw new IOException("Source '" + srcFile + "' is a directory");
          }
          if (destFile.exists()) {
              throw new FileExistsException("Destination '" + destFile + "' already exists");
          }
          if (destFile.isDirectory()) {
              throw new IOException("Destination '" + destFile + "' is a directory");
          }
          boolean rename = srcFile.renameTo(destFile);
          if (!rename) {
              copyFile( srcFile, destFile );
              if (!srcFile.delete()) {
                  FileUtils.deleteQuietly(destFile);
                  throw new IOException("Failed to delete original file '" + srcFile +
                          "' after copy to '" + destFile + "'");
              }
          }
      }
  
      /**
       * Moves a file to a directory.
       *
       * @param srcFile the file to be moved
       * @param destDir the destination file
       * @param createDestDir If {@code true} create the destination directory,
       * otherwise if {@code false} throw an IOException
       * @throws NullPointerException if source or destination is {@code null}
       * @throws FileExistsException if the destination file exists
       * @throws IOException if source or destination is invalid
       * @throws IOException if an IO error occurs moving the file
       * @since 1.4
       */
      public static void moveFileToDirectory(File srcFile, File destDir, boolean createDestDir) throws IOException {
          if (srcFile == null) {
              throw new NullPointerException("Source must not be null");
          }
          if (destDir == null) {
              throw new NullPointerException("Destination directory must not be null");
          }
          if (!destDir.exists() && createDestDir) {
              destDir.mkdirs();
          }
          if (!destDir.exists()) {
              throw new FileNotFoundException("Destination directory '" + destDir +
                      "' does not exist [createDestDir=" + createDestDir +"]");
          }
          if (!destDir.isDirectory()) {
              throw new IOException("Destination '" + destDir + "' is not a directory");
          }
          moveFile(srcFile, new File(destDir, srcFile.getName()));
      }
  
      /**
       * Moves a file or directory to the destination directory.
       * <p>
       * When the destination is on another file system, do a "copy and delete".
       *
       * @param src the file or directory to be moved
       * @param destDir the destination directory 
       * @param createDestDir If {@code true} create the destination directory,
       * otherwise if {@code false} throw an IOException
       * @throws NullPointerException if source or destination is {@code null}
       * @throws FileExistsException if the directory or file exists in the destination directory
       * @throws IOException if source or destination is invalid
       * @throws IOException if an IO error occurs moving the file
       * @since 1.4
       */
      public static void moveToDirectory(File src, File destDir, boolean createDestDir) throws IOException {
          if (src == null) {
              throw new NullPointerException("Source must not be null");
          }
          if (destDir == null) {
              throw new NullPointerException("Destination must not be null");
          }
          if (!src.exists()) {
              throw new FileNotFoundException("Source '" + src + "' does not exist");
          }
          if (src.isDirectory()) {
              moveDirectoryToDirectory(src, destDir, createDestDir);
          } else {
              moveFileToDirectory(src, destDir, createDestDir);
          }
      }
  
      /**
       * Determines whether the specified file is a Symbolic Link rather than an actual file.
       * <p>
       * Will not return true if there is a Symbolic Link anywhere in the path,
       * only if the specific file is.
       * <p>
       * <b>Note:</b> the current implementation always returns {@code false} if the system
       * is detected as Windows using {@link FilenameUtils#isSystemWindows()}
       * 
       * @param file the file to check
       * @return true if the file is a Symbolic Link
       * @throws IOException if an IO error occurs while checking the file
       * @since 2.0
       */
      public static boolean isSymlink(File file) throws IOException {
          if (file == null) {
              throw new NullPointerException("File must not be null");
          }
          if (FilenameUtils.isSystemWindows()) {
              return false;
          }
          File fileInCanonicalDir = null;
          if (file.getParent() == null) {
              fileInCanonicalDir = file;
          } else {
              File canonicalDir = file.getParentFile().getCanonicalFile();
              fileInCanonicalDir = new File(canonicalDir, file.getName());
          }
          
          if (fileInCanonicalDir.getCanonicalFile().equals(fileInCanonicalDir.getAbsoluteFile())) {
              return false;
          } else {
              return true;
          }
      }
  
  }
  