    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.io;
    018
    019import java.nio.charset.Charset;
    020import java.nio.charset.StandardCharsets;
    021import java.util.Collections;
    022import java.util.SortedMap;
    023import java.util.TreeMap;
    024
    025/**
    026 * Charsets required of every implementation of the Java platform.
    027 *
    028 * From the Java documentation <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">
    029 * Standard charsets</a>:
    030 * <p>
    031 * <cite>Every implementation of the Java platform is required to support the following character encodings. Consult
    032 * the release documentation for your implementation to see if any other encodings are supported. Consult the release
    033 * documentation for your implementation to see if any other encodings are supported. </cite>
    034 * </p>
    035 *
    036 * <ul>
    037 * <li><code>US-ASCII</code><br>
    038 * Seven-bit ASCII, a.k.a. ISO646-US, a.k.a. the Basic Latin block of the Unicode character set.</li>
    039 * <li><code>ISO-8859-1</code><br>
    040 * ISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.</li>
    041 * <li><code>UTF-8</code><br>
    042 * Eight-bit Unicode Transformation Format.</li>
    043 * <li><code>UTF-16BE</code><br>
    044 * Sixteen-bit Unicode Transformation Format, big-endian byte order.</li>
    045 * <li><code>UTF-16LE</code><br>
    046 * Sixteen-bit Unicode Transformation Format, little-endian byte order.</li>
    047 * <li><code>UTF-16</code><br>
    048 * Sixteen-bit Unicode Transformation Format, byte order specified by a mandatory initial byte-order mark (either order
    049 * accepted on input, big-endian used on output.)</li>
    050 * </ul>
    051 *
    052 * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    053 * @since 2.3
    054 *
    055 */
    056public class Charsets {
    057    //
    058    // This class should only contain Charset instances for required encodings. This guarantees that it will load
    059    // correctly and without delay on all Java platforms.
    060    //
    061
    062    /**
    063     * Constructs a sorted map from canonical charset names to charset objects required of every implementation of the
    064     * Java platform.
    065     * <p>
    066     * From the Java documentation <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">
    067     * Standard charsets</a>:
    068     * </p>
    069     *
    070     * @return An immutable, case-insensitive map from canonical charset names to charset objects.
    071     * @see Charset#availableCharsets()
    072     * @since 2.5
    073     */
    074    public static SortedMap<String, Charset> requiredCharsets() {
    075        // maybe cache?
    076        final TreeMap<String, Charset> m = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
    077        m.put(StandardCharsets.ISO_8859_1.name(), StandardCharsets.ISO_8859_1);
    078        m.put(StandardCharsets.US_ASCII.name(), StandardCharsets.US_ASCII);
    079        m.put(StandardCharsets.UTF_16.name(), StandardCharsets.UTF_16);
    080        m.put(StandardCharsets.UTF_16BE.name(), StandardCharsets.UTF_16BE);
    081        m.put(StandardCharsets.UTF_16LE.name(), StandardCharsets.UTF_16LE);
    082        m.put(StandardCharsets.UTF_8.name(), StandardCharsets.UTF_8);
    083        return Collections.unmodifiableSortedMap(m);
    084    }
    085
    086    /**
    087     * Returns the given Charset or the default Charset if the given Charset is null.
    088     *
    089     * @param charset
    090     *            A charset or null.
    091     * @return the given Charset or the default Charset if the given Charset is null
    092     */
    093    public static Charset toCharset(final Charset charset) {
    094        return charset == null ? Charset.defaultCharset() : charset;
    095    }
    096
    097    /**
    098     * Returns a Charset for the named charset. If the name is null, return the default Charset.
    099     *
    100     * @param charsetName
    101     *            The name of the requested charset, may be null.
    102     * @return a Charset for the named charset
    103     * @throws java.nio.charset.UnsupportedCharsetException
    104     *             If the named charset is unavailable
    105     */
    106    public static Charset toCharset(final String charsetName) {
    107        return charsetName == null ? Charset.defaultCharset() : Charset.forName(charsetName);
    108    }
    109
    110    /**
    111     * CharEncodingISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.
    112     * <p>
    113     * Every implementation of the Java platform is required to support this character encoding.
    114     * </p>
    115     *
    116     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    117     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    118     */
    119    @Deprecated
    120    public static final Charset ISO_8859_1 = StandardCharsets.ISO_8859_1;
    121
    122    /**
    123     * <p>
    124     * Seven-bit ASCII, also known as ISO646-US, also known as the Basic Latin block of the Unicode character set.
    125     * </p>
    126     * <p>
    127     * Every implementation of the Java platform is required to support this character encoding.
    128     * </p>
    129     *
    130     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    131     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    132     */
    133    @Deprecated
    134    public static final Charset US_ASCII = StandardCharsets.US_ASCII;
    135
    136    /**
    137     * <p>
    138     * Sixteen-bit Unicode Transformation Format, The byte order specified by a mandatory initial byte-order mark
    139     * (either order accepted on input, big-endian used on output)
    140     * </p>
    141     * <p>
    142     * Every implementation of the Java platform is required to support this character encoding.
    143     * </p>
    144     *
    145     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    146     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    147     */
    148    @Deprecated
    149    public static final Charset UTF_16 = StandardCharsets.UTF_16;
    150
    151    /**
    152     * <p>
    153     * Sixteen-bit Unicode Transformation Format, big-endian byte order.
    154     * </p>
    155     * <p>
    156     * Every implementation of the Java platform is required to support this character encoding.
    157     * </p>
    158     *
    159     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    160     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    161     */
    162    @Deprecated
    163    public static final Charset UTF_16BE = StandardCharsets.UTF_16BE;
    164
    165    /**
    166     * <p>
    167     * Sixteen-bit Unicode Transformation Format, little-endian byte order.
    168     * </p>
    169     * <p>
    170     * Every implementation of the Java platform is required to support this character encoding.
    171     * </p>
    172     *
    173     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    174     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    175     */
    176    @Deprecated
    177    public static final Charset UTF_16LE = StandardCharsets.UTF_16LE;
    178
    179    /**
    180     * <p>
    181     * Eight-bit Unicode Transformation Format.
    182     * </p>
    183     * <p>
    184     * Every implementation of the Java platform is required to support this character encoding.
    185     * </p>
    186     *
    187     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    188     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    189     */
    190    @Deprecated
    191    public static final Charset UTF_8 = StandardCharsets.UTF_8;
    192}