Java tutorial
/* * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.nio.charset.spi; import java.nio.charset.Charset; import java.util.Iterator; /** * Charset service-provider class. * * <p> A charset provider is a concrete subclass of this class that has a * zero-argument constructor and some number of associated charset * implementation classes. Charset providers may be installed in an instance * of the Java platform as extensions. Providers may also be made available by * adding them to the applet or application class path or by some other * platform-specific means. Charset providers are looked up via the current * thread's {@link java.lang.Thread#getContextClassLoader() context class * loader}. * * <p> A charset provider identifies itself with a provider-configuration file * named {@code java.nio.charset.spi.CharsetProvider} in the resource * directory {@code META-INF/services}. The file should contain a list of * fully-qualified concrete charset-provider class names, one per line. A line * is terminated by any one of a line feed ({@code '\n'}), a carriage return * ({@code '\r'}), or a carriage return followed immediately by a line feed. * Space and tab characters surrounding each name, as well as blank lines, are * ignored. The comment character is {@code '#'} (<code>'\u0023'</code>); on * each line all characters following the first comment character are ignored. * The file must be encoded in UTF-8. * * <p> If a particular concrete charset provider class is named in more than * one configuration file, or is named in the same configuration file more than * once, then the duplicates will be ignored. The configuration file naming a * particular provider need not be in the same jar file or other distribution * unit as the provider itself. The provider must be accessible from the same * class loader that was initially queried to locate the configuration file; * this is not necessarily the class loader that loaded the file. </p> * * * @author Mark Reinhold * @author JSR-51 Expert Group * @since 1.4 * * @see java.nio.charset.Charset */ public abstract class CharsetProvider { private static Void checkPermission() { SecurityManager sm = System.getSecurityManager(); if (sm != null) sm.checkPermission(new RuntimePermission("charsetProvider")); return null; } private CharsetProvider(Void ignore) { } /** * Initializes a new charset provider. * * @throws SecurityException * If a security manager has been installed and it denies * {@link RuntimePermission}{@code ("charsetProvider")} */ protected CharsetProvider() { this(checkPermission()); } /** * Creates an iterator that iterates over the charsets supported by this * provider. This method is used in the implementation of the {@link * java.nio.charset.Charset#availableCharsets Charset.availableCharsets} * method. * * @return The new iterator */ public abstract Iterator<Charset> charsets(); /** * Retrieves a charset for the given charset name. * * @param charsetName * The name of the requested charset; may be either * a canonical name or an alias * * @return A charset object for the named charset, * or {@code null} if the named charset * is not supported by this provider */ public abstract Charset charsetForName(String charsetName); }