charset.java

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    protected Charset(String canonicalName, String[] aliases) {
	checkName(canonicalName);
	String[] as = (aliases == null) ? new String[0] : aliases;
	for (int i = 0; i < as.length; i++)
	    checkName(as[i]);
	this.name = canonicalName;
	this.aliases = as;
    }

    /**
     * Returns this charset's canonical name. </p>
     *
     * @return  The canonical name of this charset
     */
    public final String name() {
	return name;
    }

    /**
     * Returns a set containing this charset's aliases. </p>
     *
     * @return  An immutable set of this charset's aliases
     */
    public final Set aliases() {
	if (aliasSet != null)
	    return aliasSet;
	int n = aliases.length;
	HashSet hs = new HashSet(n);
	for (int i = 0; i < n; i++)
	    hs.add(aliases[i]);
	aliasSet = Collections.unmodifiableSet(hs);
	return aliasSet;
    }

    /**
     * Returns this charset's human-readable name for the default locale.
     *
     * <p> The default implementation of this method simply returns this
     * charset's canonical name.  Concrete subclasses of this class may
     * override this method in order to provide a localized display name. </p>
     *
     * @return  The display name of this charset in the default locale
     */
    public String displayName() {
	return name;
    }

    /**
     * Tells whether or not this charset is registered in the <a
     * href="http://www.iana.org/assignments/character-sets">IANA Charset
     * Registry</a>.  </p>
     *
     * @return  <tt>true</tt> if, and only if, this charset is known by its
     *          implementor to be registered with the IANA
     */
    public final boolean isRegistered() {
	return !name.startsWith("X-") && !name.startsWith("x-");
    }

    /**
     * Returns this charset's human-readable name for the given locale.
     *
     * <p> The default implementation of this method simply returns this
     * charset's canonical name.  Concrete subclasses of this class may
     * override this method in order to provide a localized display name. </p>
     *
     * @param  locale
     *         The locale for which the display name is to be retrieved
     *
     * @return  The display name of this charset in the given locale
     */
    public String displayName(Locale locale) {
	return name;
    }

    /**
     * Tells whether or not this charset contains the given charset.
     *
     * <p> A charset <i>C</i> is said to <i>contain</i> a charset <i>D</i> if,
     * and only if, every character representable in <i>D</i> is also
     * representable in <i>C</i>.  If this relationship holds then it is
     * guaranteed that every string that can be encoded in <i>D</i> can also be
     * encoded in <i>C</i> without performing any replacements.
     *
     * <p> That <i>C</i> contains <i>D</i> does not imply that each character
     * representable in <i>C</i> by a particular byte sequence is represented
     * in <i>D</i> by the same byte sequence, although sometimes this is the
     * case.
     *
     * <p> Every charset contains itself.
     *
     * <p> This method computes an approximation of the containment relation:
     * If it returns <tt>true</tt> then the given charset is known to be
     * contained by this charset; if it returns <tt>false</tt>, however, then
     * it is not necessarily the case that the given charset is not contained
     * in this charset.
     *
     * @return  <tt>true</tt> if, and only if, the given charset
     *          is contained in this charset
     */
    public abstract boolean contains(Charset cs);

    /**
     * Constructs a new decoder for this charset. </p>
     *
     * @return  A new decoder for this charset
     */
    public abstract CharsetDecoder newDecoder();

    /**
     * Constructs a new encoder for this charset. </p>
     *
     * @return  A new encoder for this charset
     *
     * @throws  UnsupportedOperationException
     *          If this charset does not support encoding
     */
    public abstract CharsetEncoder newEncoder();

    /**
     * Tells whether or not this charset supports encoding.
     *
     * <p> Nearly all charsets support encoding.  The primary exceptions are
     * special-purpose <i>auto-detect</i> charsets whose decoders can determine
     * which of several possible encoding schemes is in use by examining the
     * input byte sequence.  Such charsets do not support encoding because
     * there is no way to determine which encoding should be used on output.
     * Implementations of such charsets should override this method to return
     * <tt>false</tt>. </p>
     *
     * @return  <tt>true</tt> if, and only if, this charset supports encoding
     */
    public boolean canEncode() {
	return true;
    }

    /**
     * Convenience method that decodes bytes in this charset into Unicode
     * characters.
     *
     * <p> An invocation of this method upon a charset <tt>cs</tt> returns the
     * same result as the expression
     *
     * <pre>
     *     cs.newDecoder()
     *       .onMalformedInput(CodingErrorAction.REPLACE)
     *       .onUnmappableCharacter(CodingErrorAction.REPLACE)
     *       .decode(bb); </pre>
     *
     * except that it is potentially more efficient because it can cache
     * decoders between successive invocations.
     *
     * <p> This method always replaces malformed-input and unmappable-character
     * sequences with this charset's default replacement byte array.  In order
     * to detect such sequences, use the {@link
     * CharsetDecoder#decode(java.nio.ByteBuffer)} method directly.  </p>
     *
     * @param  bb  The byte buffer to be decoded
     *
     * @return  A char buffer containing the decoded characters
     */
    public final CharBuffer decode(ByteBuffer bb) {
	try {
	    return ThreadLocalCoders.decoderFor(this)
		.onMalformedInput(CodingErrorAction.REPLACE)
		.onUnmappableCharacter(CodingErrorAction.REPLACE)
		.decode(bb);
	} catch (CharacterCodingException x) {
	    throw new Error(x);		// Can't happen
	}
    }

    /**
     * Convenience method that encodes Unicode characters into bytes in this
     * charset.
     *
     * <p> An invocation of this method upon a charset <tt>cs</tt> returns the
     * same result as the expression
     *
     * <pre>
     *     cs.newEncoder()
     *       .onMalformedInput(CodingErrorAction.REPLACE)
     *       .onUnmappableCharacter(CodingErrorAction.REPLACE)
     *       .encode(bb); </pre>
     *
     * except that it is potentially more efficient because it can cache
     * encoders between successive invocations.
     *
     * <p> This method always replaces malformed-input and unmappable-character
     * sequences with this charset's default replacement string.  In order to
     * detect such sequences, use the {@link
     * CharsetEncoder#encode(java.nio.CharBuffer)} method directly.  </p>
     *
     * @param  cb  The char buffer to be encoded
     *
     * @return  A byte buffer containing the encoded characters
     */
    public final ByteBuffer encode(CharBuffer cb) {
	try {
	    return ThreadLocalCoders.encoderFor(this)
		.onMalformedInput(CodingErrorAction.REPLACE)
		.onUnmappableCharacter(CodingErrorAction.REPLACE)
		.encode(cb);
	} catch (CharacterCodingException x) {
	    throw new Error(x);		// Can't happen
	}
    }

    /**
     * Convenience method that encodes a string into bytes in this charset.
     *
     * <p> An invocation of this method upon a charset <tt>cs</tt> returns the
     * same result as the expression
     *
     * <pre>
     *     cs.encode(CharBuffer.wrap(s)); </pre>
     *
     * @param  str  The string to be encoded
     *
     * @return  A byte buffer containing the encoded characters
     */
    public final ByteBuffer encode(String str) {
	return encode(CharBuffer.wrap(str));
    }

    /**
     * Compares this charset to another object.
     *
     * <p> Charsets are ordered by their canonical names, without regard to
     * case. </p>
     *
     * @param  ob
     *         The object to which this object is to be compared
     *
     * @return A negative integer, zero, or a positive integer as this charset
     *         is less than, equal to, or greater than the specified object
     */
    public final int compareTo(Object ob) {
	return (name().compareToIgnoreCase(((Charset)ob).name()));
    }

    /**
     * Computes a hashcode for this charset. </p>
     *
     * @return  An integer hashcode
     */
    public final int hashCode() {
	return name().hashCode();
    }

    /**
     * Tells whether or not this object is equal to another.
     *
     * <p> Two charsets are equal if, and only if, they have the same canonical
     * names.  A charset is never equal to any other type of object.  </p>
     *
     * @return  <tt>true</tt> if, and only if, this charset is equal to the
     *          given object
     */
    public final boolean equals(Object ob) {
	if (!(ob instanceof Charset))
	    return false;
	if (this == ob)
	    return true;
	return name.equals(((Charset)ob).name());
    }

    /**
     * Returns a string describing this charset. </p>
     *
     * @return  A string describing this charset
     */
    public final String toString() {
	return name();
    }

}