001 /*
002 * Copyright 2000-2004 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025
026 package java.nio.charset.spi;
027
028 import java.nio.charset.Charset;
029 import java.util.Iterator;
030
031 /**
032 * Charset service-provider class.
033 *
034 * <p> A charset provider is a concrete subclass of this class that has a
035 * zero-argument constructor and some number of associated charset
036 * implementation classes. Charset providers may be installed in an instance
037 * of the Java platform as extensions, that is, jar files placed into any of
038 * the usual extension directories. Providers may also be made available by
039 * adding them to the applet or application class path or by some other
040 * platform-specific means. Charset providers are looked up via the current
041 * thread's {@link java.lang.Thread#getContextClassLoader() </code>context
042 * class loader<code>}.
043 *
044 * <p> A charset provider identifies itself with a provider-configuration file
045 * named <tt>java.nio.charset.spi.CharsetProvider</tt> in the resource
046 * directory <tt>META-INF/services</tt>. The file should contain a list of
047 * fully-qualified concrete charset-provider class names, one per line. A line
048 * is terminated by any one of a line feed (<tt>'\n'</tt>), a carriage return
049 * (<tt>'\r'</tt>), or a carriage return followed immediately by a line feed.
050 * Space and tab characters surrounding each name, as well as blank lines, are
051 * ignored. The comment character is <tt>'#'</tt> (<tt>'\u0023'</tt>); on
052 * each line all characters following the first comment character are ignored.
053 * The file must be encoded in UTF-8.
054 *
055 * <p> If a particular concrete charset provider class is named in more than
056 * one configuration file, or is named in the same configuration file more than
057 * once, then the duplicates will be ignored. The configuration file naming a
058 * particular provider need not be in the same jar file or other distribution
059 * unit as the provider itself. The provider must be accessible from the same
060 * class loader that was initially queried to locate the configuration file;
061 * this is not necessarily the class loader that loaded the file. </p>
062 *
063 *
064 * @author Mark Reinhold
065 * @author JSR-51 Expert Group
066 * @version 1.22, 07/05/05
067 * @since 1.4
068 *
069 * @see java.nio.charset.Charset
070 */
071
072 public abstract class CharsetProvider {
073
074 /**
075 * Initializes a new charset provider. </p>
076 *
077 * @throws SecurityException
078 * If a security manager has been installed and it denies
079 * {@link RuntimePermission}<tt>("charsetProvider")</tt>
080 */
081 protected CharsetProvider() {
082 SecurityManager sm = System.getSecurityManager();
083 if (sm != null)
084 sm
085 .checkPermission(new RuntimePermission(
086 "charsetProvider"));
087 }
088
089 /**
090 * Creates an iterator that iterates over the charsets supported by this
091 * provider. This method is used in the implementation of the {@link
092 * java.nio.charset.Charset#availableCharsets Charset.availableCharsets}
093 * method. </p>
094 *
095 * @return The new iterator
096 */
097 public abstract Iterator<Charset> charsets();
098
099 /**
100 * Retrieves a charset for the given charset name. </p>
101 *
102 * @param charsetName
103 * The name of the requested charset; may be either
104 * a canonical name or an alias
105 *
106 * @return A charset object for the named charset,
107 * or <tt>null</tt> if the named charset
108 * is not supported by this provider
109 */
110 public abstract Charset charsetForName(String charsetName);
111
112 }
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