    001    /*
    002     * Licensed to the Apache Software Foundation (ASF) under one or more
    003     * contributor license agreements.  See the NOTICE file distributed with
    004     * this work for additional information regarding copyright ownership.
    005     * The ASF licenses this file to You under the Apache License, Version 2.0
    006     * (the "License"); you may not use this file except in compliance with
    007     * the License.  You may obtain a copy of the License at
    008     *
    009     *      http://www.apache.org/licenses/LICENSE-2.0
    010     *
    011     * Unless required by applicable law or agreed to in writing, software
    012     * distributed under the License is distributed on an "AS IS" BASIS,
    013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014     * See the License for the specific language governing permissions and
    015     * limitations under the License.
    016     */
    017    package org.apache.commons.codec;
    018
    019    import java.nio.charset.Charset;
    020
    021    /**
    022     * Charsets required of every implementation of the Java platform.
    023     *
    024     * From the Java documentation <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard
    025     * charsets</a>:
    026     * <p>
    027     * <cite>Every implementation of the Java platform is required to support the following character encodings. Consult the
    028     * release documentation for your implementation to see if any other encodings are supported. Consult the release
    029     * documentation for your implementation to see if any other encodings are supported. </cite>
    030     * </p>
    031     *
    032     * <ul>
    033     * <li><code>US-ASCII</code><br/>
    034     * Seven-bit ASCII, a.k.a. ISO646-US, a.k.a. the Basic Latin block of the Unicode character set.</li>
    035     * <li><code>ISO-8859-1</code><br/>
    036     * ISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.</li>
    037     * <li><code>UTF-8</code><br/>
    038     * Eight-bit Unicode Transformation Format.</li>
    039     * <li><code>UTF-16BE</code><br/>
    040     * Sixteen-bit Unicode Transformation Format, big-endian byte order.</li>
    041     * <li><code>UTF-16LE</code><br/>
    042     * Sixteen-bit Unicode Transformation Format, little-endian byte order.</li>
    043     * <li><code>UTF-16</code><br/>
    044     * Sixteen-bit Unicode Transformation Format, byte order specified by a mandatory initial byte-order mark (either order
    045     * accepted on input, big-endian used on output.)</li>
    046     * </ul>
    047     *
    048     * This perhaps would best belong in the Commons Lang project. Even if a similar class is defined in Commons Lang, it is
    049     * not foreseen that Commons Codec would be made to depend on Commons Lang.
    050     *
    051     * <p>
    052     * This class is immutable and thread-safe.
    053     * </p>
    054     *
    055     * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    056     * @since 1.7
    057     * @version $Id: CharEncoding.java 1173287 2011-09-20 18:16:19Z ggregory $
    058     */
    059    public class Charsets {
    060
    061        //
    062        // This class should only contain Charset instances for required encodings. This guarantees that it will load
    063        // correctly and without delay on all Java platforms.
    064        //
    065
    066        /**
    067         * Returns the given Charset or the default Charset if the given Charset is null.
    068         *
    069         * @param charset
    070         *            A charset or null.
    071         * @return the given Charset or the default Charset if the given Charset is null
    072         */
    073        public static Charset toCharset(final Charset charset) {
    074            return charset == null ? Charset.defaultCharset() : charset;
    075        }
    076
    077        /**
    078         * Returns a Charset for the named charset. If the name is null, return the default Charset.
    079         *
    080         * @param charset
    081         *            The name of the requested charset, may be null.
    082         * @return a Charset for the named charset
    083         * @throws java.nio.charset.UnsupportedCharsetException
    084         *             If the named charset is unavailable
    085         */
    086        public static Charset toCharset(final String charset) {
    087            return charset == null ? Charset.defaultCharset() : Charset.forName(charset);
    088        }
    089
    090        /**
    091         * CharEncodingISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.
    092         * <p>
    093         * Every implementation of the Java platform is required to support this character encoding.
    094         *
    095         * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    096         */
    097        public static final Charset ISO_8859_1 = Charset.forName(CharEncoding.ISO_8859_1);
    098
    099        /**
    100         * Seven-bit ASCII, also known as ISO646-US, also known as the Basic Latin block of the Unicode character set.
    101         * <p>
    102         * Every implementation of the Java platform is required to support this character encoding.
    103         *
    104         * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    105         */
    106        public static final Charset US_ASCII = Charset.forName(CharEncoding.US_ASCII);
    107
    108        /**
    109         * Sixteen-bit Unicode Transformation Format, The byte order specified by a mandatory initial byte-order mark
    110         * (either order accepted on input, big-endian used on output)
    111         * <p>
    112         * Every implementation of the Java platform is required to support this character encoding.
    113         *
    114         * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    115         */
    116        public static final Charset UTF_16 = Charset.forName(CharEncoding.UTF_16);
    117
    118        /**
    119         * Sixteen-bit Unicode Transformation Format, big-endian byte order.
    120         * <p>
    121         * Every implementation of the Java platform is required to support this character encoding.
    122         *
    123         * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    124         */
    125        public static final Charset UTF_16BE = Charset.forName(CharEncoding.UTF_16BE);
    126
    127        /**
    128         * Sixteen-bit Unicode Transformation Format, little-endian byte order.
    129         * <p>
    130         * Every implementation of the Java platform is required to support this character encoding.
    131         *
    132         * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    133         */
    134        public static final Charset UTF_16LE = Charset.forName(CharEncoding.UTF_16LE);
    135
    136        /**
    137         * Eight-bit Unicode Transformation Format.
    138         * <p>
    139         * Every implementation of the Java platform is required to support this character encoding.
    140         *
    141         * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    142         */
    143        public static final Charset UTF_8 = Charset.forName(CharEncoding.UTF_8);
    144    }