    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 */
    017package org.apache.commons.codec;
    018
    019import 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><p>
    034 * Seven-bit ASCII, a.k.a. ISO646-US, a.k.a. the Basic Latin block of the Unicode character set.</p></li>
    035 * <li><code>ISO-8859-1</code><p>
    036 * ISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.</p></li>
    037 * <li><code>UTF-8</code><p>
    038 * Eight-bit Unicode Transformation Format.</p></li>
    039 * <li><code>UTF-16BE</code><p>
    040 * Sixteen-bit Unicode Transformation Format, big-endian byte order.</p></li>
    041 * <li><code>UTF-16LE</code><p>
    042 * Sixteen-bit Unicode Transformation Format, little-endian byte order.</p></li>
    043 * <li><code>UTF-16</code><p>
    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.)</p></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 */
    058public class Charsets {
    059
    060    //
    061    // This class should only contain Charset instances for required encodings. This guarantees that it will load
    062    // correctly and without delay on all Java platforms.
    063    //
    064
    065    /**
    066     * Returns the given Charset or the default Charset if the given Charset is null.
    067     *
    068     * @param charset
    069     *            A charset or null.
    070     * @return the given Charset or the default Charset if the given Charset is null
    071     */
    072    public static Charset toCharset(final Charset charset) {
    073        return charset == null ? Charset.defaultCharset() : charset;
    074    }
    075
    076    /**
    077     * Returns a Charset for the named charset. If the name is null, return the default Charset.
    078     *
    079     * @param charset
    080     *            The name of the requested charset, may be null.
    081     * @return a Charset for the named charset
    082     * @throws java.nio.charset.UnsupportedCharsetException
    083     *             If the named charset is unavailable
    084     */
    085    public static Charset toCharset(final String charset) {
    086        return charset == null ? Charset.defaultCharset() : Charset.forName(charset);
    087    }
    088
    089    /**
    090     * CharEncodingISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.
    091     * <p>
    092     * Every implementation of the Java platform is required to support this character encoding.
    093     * </p>
    094     * <p>
    095     * On Java 7 or later, use {@link java.nio.charset.StandardCharsets#ISO_8859_1} instead.
    096     * </p>
    097     *
    098     * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    099     */
    100    public static final Charset ISO_8859_1 = Charset.forName(CharEncoding.ISO_8859_1);
    101
    102    /**
    103     * Seven-bit ASCII, also known as ISO646-US, also known as the Basic Latin block of the Unicode character set.
    104     * <p>
    105     * Every implementation of the Java platform is required to support this character encoding.
    106     * </p>
    107     * <p>
    108     * On Java 7 or later, use {@link java.nio.charset.StandardCharsets#ISO_8859_1} instead.
    109     * </p>
    110     *
    111     * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    112     */
    113    public static final Charset US_ASCII = Charset.forName(CharEncoding.US_ASCII);
    114
    115    /**
    116     * Sixteen-bit Unicode Transformation Format, The byte order specified by a mandatory initial byte-order mark
    117     * (either order accepted on input, big-endian used on output)
    118     * <p>
    119     * Every implementation of the Java platform is required to support this character encoding.
    120     * </p>
    121     * <p>
    122     * On Java 7 or later, use {@link java.nio.charset.StandardCharsets#ISO_8859_1} instead.
    123     * </p>
    124     *
    125     * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    126     */
    127    public static final Charset UTF_16 = Charset.forName(CharEncoding.UTF_16);
    128
    129    /**
    130     * Sixteen-bit Unicode Transformation Format, big-endian byte order.
    131     * <p>
    132     * Every implementation of the Java platform is required to support this character encoding.
    133     * </p>
    134     * <p>
    135     * On Java 7 or later, use {@link java.nio.charset.StandardCharsets#ISO_8859_1} instead.
    136     * </p>
    137     *
    138     * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    139     */
    140    public static final Charset UTF_16BE = Charset.forName(CharEncoding.UTF_16BE);
    141
    142    /**
    143     * Sixteen-bit Unicode Transformation Format, little-endian byte order.
    144     * <p>
    145     * Every implementation of the Java platform is required to support this character encoding.
    146     * </p>
    147     * <p>
    148     * On Java 7 or later, use {@link java.nio.charset.StandardCharsets#ISO_8859_1} instead.
    149     * </p>
    150     *
    151     * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    152     */
    153    public static final Charset UTF_16LE = Charset.forName(CharEncoding.UTF_16LE);
    154
    155    /**
    156     * Eight-bit Unicode Transformation Format.
    157     * <p>
    158     * Every implementation of the Java platform is required to support this character encoding.
    159     * </p>
    160     * <p>
    161     * On Java 7 or later, use {@link java.nio.charset.StandardCharsets#ISO_8859_1} instead.
    162     * </p>
    163     *
    164     * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    165     */
    166    public static final Charset UTF_8 = Charset.forName(CharEncoding.UTF_8);
    167}