content: package com.ctrip.framework.apollo.core.utils;
  
  import java.util.Collection;
  import java.util.Iterator;
  
  public class StringUtils {
  
    public static final String EMPTY = "";
  
    /**
     * <p>
     * Checks if a String is empty ("") or null.
     * </p>
     *
     * <pre>
     * StringUtils.isEmpty(null)      = true
     * StringUtils.isEmpty("")        = true
     * StringUtils.isEmpty(" ")       = false
     * StringUtils.isEmpty("bob")     = false
     * StringUtils.isEmpty("  bob  ") = false
     * </pre>
     *
     * <p>
     * NOTE: This method changed in Lang version 2.0. It no longer trims the String. That functionality is available in isBlank().
     * </p>
     *
     * @param str the String to check, may be null
     * @return <code>true</code> if the String is empty or null
     */
    public static boolean isEmpty(String str) {
      return str == null || str.length() == 0;
    }
  
  
    public static boolean isContainEmpty(String... args){
      if (args == null){
        return false;
      }
  
      for (String arg: args){
        if (arg == null || "".equals(arg)){
          return true;
        }
      }
  
      return false;
    }
    /**
     * <p>
     * Checks if a String is whitespace, empty ("") or null.
     * </p>
     *
     * <pre>
     * StringUtils.isBlank(null)      = true
     * StringUtils.isBlank("")        = true
     * StringUtils.isBlank(" ")       = true
     * StringUtils.isBlank("bob")     = false
     * StringUtils.isBlank("  bob  ") = false
     * </pre>
     *
     * @param str the String to check, may be null
     * @return <code>true</code> if the String is null, empty or whitespace
     */
    public static boolean isBlank(String str) {
      int strLen;
      if (str == null || (strLen = str.length()) == 0) {
        return true;
      }
      for (int i = 0; i < strLen; i++) {
        if (Character.isWhitespace(str.charAt(i)) == false) {
          return false;
        }
      }
      return true;
    }
  
    /**
     * <p>
     * Removes control characters (char &lt;= 32) from both ends of this String returning <code>null</code> if the String is empty
     * ("") after the trim or if it is <code>null</code>.
     *
     * <p>
     * The String is trimmed using {@link String#trim()}. Trim removes start and end characters &lt;= 32. To strip whitespace use
     * {@link #stripToNull(String)}.
     * </p>
     *
     * <pre>
     * StringUtils.trimToNull(null)          = null
     * StringUtils.trimToNull("")            = null
     * StringUtils.trimToNull("     ")       = null
     * StringUtils.trimToNull("abc")         = "abc"
     * StringUtils.trimToNull("    abc    ") = "abc"
     * </pre>
     *
     * @param str the String to be trimmed, may be null
     * @return the trimmed String, <code>null</code> if only chars &lt;= 32, empty or null String input
     * @since 2.0
     */
    public static String trimToNull(String str) {
      String ts = trim(str);
      return isEmpty(ts) ? null : ts;
    }
  
    /**
     * <p>
     * Removes control characters (char &lt;= 32) from both ends of this String returning an empty String ("") if the String is empty
     * ("") after the trim or if it is <code>null</code>.
     *
     * <p>
     * The String is trimmed using {@link String#trim()}. Trim removes start and end characters &lt;= 32. To strip whitespace use
     * {@link #stripToEmpty(String)}.
     * </p>
     *
     * <pre>
     * StringUtils.trimToEmpty(null)          = ""
     * StringUtils.trimToEmpty("")            = ""
     * StringUtils.trimToEmpty("     ")       = ""
     * StringUtils.trimToEmpty("abc")         = "abc"
     * StringUtils.trimToEmpty("    abc    ") = "abc"
     * </pre>
     *
     * @param str the String to be trimmed, may be null
     * @return the trimmed String, or an empty String if <code>null</code> input
     * @since 2.0
     */
    public static String trimToEmpty(String str) {
      return str == null ? EMPTY : str.trim();
    }
  
    /**
     * <p>
     * Removes control characters (char &lt;= 32) from both ends of this String, handling <code>null</code> by returning
     * <code>null</code>.
     * </p>
     *
     * <p>
     * The String is trimmed using {@link String#trim()}. Trim removes start and end characters &lt;= 32. To strip whitespace use
     * {@link #strip(String)}.
     * </p>
     *
     * <p>
     * To trim your choice of characters, use the {@link #strip(String, String)} methods.
     * </p>
     *
     * <pre>
     * StringUtils.trim(null)          = null
     * StringUtils.trim("")            = ""
     * StringUtils.trim("     ")       = ""
     * StringUtils.trim("abc")         = "abc"
     * StringUtils.trim("    abc    ") = "abc"
     * </pre>
     *
     * @param str the String to be trimmed, may be null
     * @return the trimmed string, <code>null</code> if null String input
     */
    public static String trim(String str) {
      return str == null ? null : str.trim();
    }
  
    /**
     * <p>
     * Compares two Strings, returning <code>true</code> if they are equal.
     * </p>
     *
     * <p>
     * <code>null</code>s are handled without exceptions. Two <code>null</code> references are considered to be equal. The comparison
     * is case sensitive.
     * </p>
     *
     * <pre>
     * StringUtils.equals(null, null)   = true
     * StringUtils.equals(null, "abc")  = false
     * StringUtils.equals("abc", null)  = false
     * StringUtils.equals("abc", "abc") = true
     * StringUtils.equals("abc", "ABC") = false
     * </pre>
     *
     * @param str1 the first String, may be null
     * @param str2 the second String, may be null
     * @return <code>true</code> if the Strings are equal, case sensitive, or both <code>null</code>
     * @see java.lang.String#equals(Object)
     */
    public static boolean equals(String str1, String str2) {
      return str1 == null ? str2 == null : str1.equals(str2);
    }
  
    /**
     * <p>
     * Compares two Strings, returning <code>true</code> if they are equal ignoring the case.
     * </p>
     *
     * <p>
     * <code>null</code>s are handled without exceptions. Two <code>null</code> references are considered equal. Comparison is case
     * insensitive.
     * </p>
     *
     * <pre>
     * StringUtils.equalsIgnoreCase(null, null)   = true
     * StringUtils.equalsIgnoreCase(null, "abc")  = false
     * StringUtils.equalsIgnoreCase("abc", null)  = false
     * StringUtils.equalsIgnoreCase("abc", "abc") = true
     * StringUtils.equalsIgnoreCase("abc", "ABC") = true
     * </pre>
     *
     * @param str1 the first String, may be null
     * @param str2 the second String, may be null
     * @return <code>true</code> if the Strings are equal, case insensitive, or both <code>null</code>
     * @see java.lang.String#equalsIgnoreCase(String)
     */
    public static boolean equalsIgnoreCase(String str1, String str2) {
      return str1 == null ? str2 == null : str1.equalsIgnoreCase(str2);
    }
  
    /**
     * <p>
     * Check if a String starts with a specified prefix.
     * </p>
     *
     * <p>
     * <code>null</code>s are handled without exceptions. Two <code>null</code> references are considered to be equal. The comparison
     * is case sensitive.
     * </p>
     *
     * <pre>
     * StringUtils.startsWith(null, null)      = true
     * StringUtils.startsWith(null, "abc")     = false
     * StringUtils.startsWith("abcdef", null)  = false
     * StringUtils.startsWith("abcdef", "abc") = true
     * StringUtils.startsWith("ABCDEF", "abc") = false
     * </pre>
     *
     * @param str    the String to check, may be null
     * @param prefix the prefix to find, may be null
     * @return <code>true</code> if the String starts with the prefix, case sensitive, or both <code>null</code>
     * @see java.lang.String#startsWith(String)
     * @since 2.4
     */
    public static boolean startsWith(String str, String prefix) {
      return startsWith(str, prefix, false);
    }
  
    /**
     * <p>
     * Check if a String starts with a specified prefix (optionally case insensitive).
     * </p>
     *
     * @param str        the String to check, may be null
     * @param prefix     the prefix to find, may be null
     * @param ignoreCase inidicates whether the compare should ignore case (case insensitive) or not.
     * @return <code>true</code> if the String starts with the prefix or both <code>null</code>
     * @see java.lang.String#startsWith(String)
     */
    private static boolean startsWith(String str, String prefix, boolean ignoreCase) {
      if (str == null || prefix == null) {
        return str == null && prefix == null;
      }
      if (prefix.length() > str.length()) {
        return false;
      }
      return str.regionMatches(ignoreCase, 0, prefix, 0, prefix.length());
    }
  
    /**
     * <p>
     * Case insensitive check if a String starts with a specified prefix.
     * </p>
     *
     * <p>
     * <code>null</code>s are handled without exceptions. Two <code>null</code> references are considered to be equal. The comparison
     * is case insensitive.
     * </p>
     *
     * <pre>
     * StringUtils.startsWithIgnoreCase(null, null)      = true
     * StringUtils.startsWithIgnoreCase(null, "abc")     = false
     * StringUtils.startsWithIgnoreCase("abcdef", null)  = false
     * StringUtils.startsWithIgnoreCase("abcdef", "abc") = true
     * StringUtils.startsWithIgnoreCase("ABCDEF", "abc") = true
     * </pre>
     *
     * @param str    the String to check, may be null
     * @param prefix the prefix to find, may be null
     * @return <code>true</code> if the String starts with the prefix, case insensitive, or both <code>null</code>
     * @see java.lang.String#startsWith(String)
     * @since 2.4
     */
    public static boolean startsWithIgnoreCase(String str, String prefix) {
      return startsWith(str, prefix, true);
    }
  
    /**
     * <p>
     * Checks if the String contains only unicode digits. A decimal point is not a unicode digit and returns false.
     * </p>
     *
     * <p>
     * <code>null</code> will return <code>false</code>. An empty String (length()=0) will return <code>true</code>.
     * </p>
     *
     * <pre>
     * StringUtils.isNumeric(null)   = false
     * StringUtils.isNumeric("")     = true
     * StringUtils.isNumeric("  ")   = false
     * StringUtils.isNumeric("123")  = true
     * StringUtils.isNumeric("12 3") = false
     * StringUtils.isNumeric("ab2c") = false
     * StringUtils.isNumeric("12-3") = false
     * StringUtils.isNumeric("12.3") = false
     * </pre>
     *
     * @param str the String to check, may be null
     * @return <code>true</code> if only contains digits, and is non-null
     */
    public static boolean isNumeric(String str) {
      if (str == null) {
        return false;
      }
      int sz = str.length();
      for (int i = 0; i < sz; i++) {
        if (Character.isDigit(str.charAt(i)) == false) {
          return false;
        }
      }
      return true;
    }
  
    public static interface StringFormatter<T> {
      String format(T obj);
    }
  
    public static <T> String join(Collection<T> collection, String separator) {
      return join(collection, separator, new StringFormatter<T>() {
        @Override
        public String format(T obj) {
          return obj.toString();
        }
      });
    }
  
    public static <T> String join(Collection<T> collection, String separator,
                                  StringFormatter<T> formatter) {
      Iterator<T> iterator = collection.iterator();
      // handle null, zero and one elements before building a buffer
      if (iterator == null) {
        return null;
      }
      if (!iterator.hasNext()) {
        return EMPTY;
      }
      T first = iterator.next();
      if (!iterator.hasNext()) {
        return first == null ? "" : formatter.format(first);
      }
  
      // two or more elements
      StringBuilder buf = new StringBuilder(256); // Java default is 16, probably too small
      if (first != null) {
        buf.append(formatter.format(first));
      }
  
      while (iterator.hasNext()) {
        buf.append(separator);
        T obj = iterator.next();
        if (obj != null) {
          buf.append(formatter.format(obj));
        }
      }
  
      return buf.toString();
    }
  }
  