content: package com.alipay.api.internal.util.file;
  
  import java.nio.charset.Charset;
  import java.util.Collections;
  import java.util.SortedMap;
  import java.util.TreeMap;
  
  public class Charsets {
  
      //
      // This class should only contain Charset instances for required encodings. This guarantees that it will load
      // correctly and without delay on all Java platforms.
      //
  
      /**
       * Constructs a sorted map from canonical charset names to charset objects required of every implementation of the Java platform.
       * <p>
       * From the Java documentation <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html"> Standard charsets</a>:
       * </p>
       *
       * @return An immutable, case-insensitive map from canonical charset names to charset objects.
       * @see Charset#availableCharsets()
       * @since 2.5
       */
      public static SortedMap<String, Charset> requiredCharsets() {
          // maybe cache?
          // TODO Re-implement on Java 7 to use java.nio.charset.StandardCharsets
          final TreeMap<String, Charset> m = new TreeMap<String, Charset>(String.CASE_INSENSITIVE_ORDER);
          m.put(ISO_8859_1.name(), ISO_8859_1);
          m.put(US_ASCII.name(), US_ASCII);
          m.put(UTF_16.name(), UTF_16);
          m.put(UTF_16BE.name(), UTF_16BE);
          m.put(UTF_16LE.name(), UTF_16LE);
          m.put(UTF_8.name(), UTF_8);
          return Collections.unmodifiableSortedMap(m);
      }
  
      /**
       * Returns the given Charset or the default Charset if the given Charset is null.
       *
       * @param charset A charset or null.
       * @return the given Charset or the default Charset if the given Charset is null
       */
      public static Charset toCharset(final Charset charset) {
          return charset == null ? Charset.defaultCharset() : charset;
      }
  
      /**
       * Returns a Charset for the named charset. If the name is null, return the default Charset.
       *
       * @param charset The name of the requested charset, may be null.
       * @return a Charset for the named charset
       * @throws java.nio.charset.UnsupportedCharsetException If the named charset is unavailable
       */
      public static Charset toCharset(final String charset) {
          return charset == null ? Charset.defaultCharset() : Charset.forName(charset);
      }
  
      /**
       * CharEncodingISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.
       * <p>
       * Every implementation of the Java platform is required to support this character encoding.
       * </p>
       *
       * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
       * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
       */
      @Deprecated
      public static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");
  
      /**
       * <p>
       * Seven-bit ASCII, also known as ISO646-US, also known as the Basic Latin block of the Unicode character set.
       * </p>
       * <p>
       * Every implementation of the Java platform is required to support this character encoding.
       * </p>
       *
       * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
       * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
       */
      @Deprecated
      public static final Charset US_ASCII = Charset.forName("US-ASCII");
  
      /**
       * <p>
       * Sixteen-bit Unicode Transformation Format, The byte order specified by a mandatory initial byte-order mark (either order accepted on
       * input, big-endian used on output)
       * </p>
       * <p>
       * Every implementation of the Java platform is required to support this character encoding.
       * </p>
       *
       * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
       * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
       */
      @Deprecated
      public static final Charset UTF_16 = Charset.forName("UTF-16");
  
      /**
       * <p>
       * Sixteen-bit Unicode Transformation Format, big-endian byte order.
       * </p>
       * <p>
       * Every implementation of the Java platform is required to support this character encoding.
       * </p>
       *
       * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
       * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
       */
      @Deprecated
      public static final Charset UTF_16BE = Charset.forName("UTF-16BE");
  
      /**
       * <p>
       * Sixteen-bit Unicode Transformation Format, little-endian byte order.
       * </p>
       * <p>
       * Every implementation of the Java platform is required to support this character encoding.
       * </p>
       *
       * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
       * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
       */
      @Deprecated
      public static final Charset UTF_16LE = Charset.forName("UTF-16LE");
  
      /**
       * <p>
       * Eight-bit Unicode Transformation Format.
       * </p>
       * <p>
       * Every implementation of the Java platform is required to support this character encoding.
       * </p>
       *
       * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
       * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
       */
      @Deprecated
      public static final Charset UTF_8 = Charset.forName("UTF-8");
  }
  