/* Provider.java --    Copyright (C) 2002 Free Software Foundation, Inc.This file is part of GNU Classpath.GNU Classpath is free software; you can redistribute it and/or modifyit under the terms of the GNU General Public License as published bythe Free Software Foundation; either version 2, or (at your option)any later version.GNU Classpath is distributed in the hope that it will be useful, butWITHOUT ANY WARRANTY; without even the implied warranty ofMERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNUGeneral Public License for more details.You should have received a copy of the GNU General Public Licensealong with GNU Classpath; see the file COPYING.  If not, write to theFree Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA02111-1307 USA.Linking this library statically or dynamically with other modules ismaking a combined work based on this library.  Thus, the terms andconditions of the GNU General Public License cover the wholecombination.As a special exception, the copyright holders of this library give youpermission to link this library with independent modules to produce anexecutable, regardless of the license terms of these independentmodules, and to copy and distribute the resulting executable underterms of your choice, provided that you also meet, for each linkedindependent module, the terms and conditions of the license of thatmodule.  An independent module is a module which is not derived fromor based on this library.  If you modify this library, you may extendthis exception to your version of the library, but you are notobligated to do so.  If you do not wish to do so, delete thisexception statement from your version. */package gnu.java.nio.charset;import java.nio.charset.Charset;import java.nio.charset.spi.CharsetProvider;import java.util.Collections;import java.util.HashMap;import java.util.Iterator;/** * Charset provider for the required charsets.  Used by * {@link Charset#charsetForName} and * {@link Charset#availableCharsets}. * * @author Jesse Rosenstock * @see Charset */public final class Provider extends CharsetProvider{  private static Provider singleton;  static  {    synchronized (Provider.class)      {        singleton = null;      }  }  /**   * Map from charset name to charset canonical name.   */  private final HashMap canonicalNames;  /**   * Map from canonical name to Charset.   * TODO: We may want to use soft references.  We would then need to keep   * track of the class name to regenerate the object.   */  private final HashMap charsets;  private Provider ()  {    // FIXME: We might need to make the name comparison case insensitive.    // Verify this with the Sun JDK.    canonicalNames = new HashMap ();    charsets = new HashMap ();    // US-ASCII aka ISO646-US    addCharset (new US_ASCII ());    // ISO-8859-1 aka ISO-LATIN-1    addCharset (new ISO_8859_1 ());    // UTF-8    addCharset (new UTF_8 ());    // UTF-16BE    addCharset (new UTF_16BE ());    // UTF-16LE    addCharset (new UTF_16LE ());    // UTF-16    addCharset (new UTF_16 ());  }  public Iterator charsets ()  {    return Collections.unmodifiableCollection (charsets.values ())                      .iterator ();  }  public Charset charsetForName (String charsetName)  {    return (Charset) charsets.get (canonicalize (charsetName));  }  private Object canonicalize (String charsetName)  {    Object o = canonicalNames.get (charsetName);    return o == null ? charsetName : o;  }  private void addCharset (Charset cs)  {    String canonicalName = cs.name ();    charsets.put (canonicalName, cs);    for (Iterator i = cs.aliases ().iterator (); i.hasNext (); )      canonicalNames.put (i.next (), canonicalName);  }  public static synchronized Provider provider ()  {    if (singleton == null)      singleton = new Provider ();    return singleton;  }}