    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 */
    055public class Charsets {
    056
    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    private static final SortedMap<String, Charset> STANDARD_CHARSET_MAP;
    063
    064    static {
    065        final SortedMap<String, Charset> standardCharsetMap = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
    066        standardCharsetMap.put(StandardCharsets.ISO_8859_1.name(), StandardCharsets.ISO_8859_1);
    067        standardCharsetMap.put(StandardCharsets.US_ASCII.name(), StandardCharsets.US_ASCII);
    068        standardCharsetMap.put(StandardCharsets.UTF_16.name(), StandardCharsets.UTF_16);
    069        standardCharsetMap.put(StandardCharsets.UTF_16BE.name(), StandardCharsets.UTF_16BE);
    070        standardCharsetMap.put(StandardCharsets.UTF_16LE.name(), StandardCharsets.UTF_16LE);
    071        standardCharsetMap.put(StandardCharsets.UTF_8.name(), StandardCharsets.UTF_8);
    072        STANDARD_CHARSET_MAP = Collections.unmodifiableSortedMap(standardCharsetMap);
    073    }
    074
    075    /**
    076     * Constructs a sorted map from canonical charset names to charset objects required of every implementation of the
    077     * Java platform.
    078     * <p>
    079     * From the Java documentation <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">
    080     * Standard charsets</a>:
    081     * </p>
    082     *
    083     * @return An immutable, case-insensitive map from canonical charset names to charset objects.
    084     * @see Charset#availableCharsets()
    085     * @since 2.5
    086     */
    087    public static SortedMap<String, Charset> requiredCharsets() {
    088        return STANDARD_CHARSET_MAP;
    089    }
    090
    091    /**
    092     * Returns the given Charset or the default Charset if the given Charset is null.
    093     *
    094     * @param charset
    095     *            A charset or null.
    096     * @return the given Charset or the default Charset if the given Charset is null
    097     */
    098    public static Charset toCharset(final Charset charset) {
    099        return charset == null ? Charset.defaultCharset() : charset;
    100    }
    101
    102    /**
    103     * Returns a Charset for the named charset. If the name is null, return the default Charset.
    104     *
    105     * @param charsetName
    106     *            The name of the requested charset, may be null.
    107     * @return a Charset for the named charset
    108     * @throws java.nio.charset.UnsupportedCharsetException
    109     *             If the named charset is unavailable
    110     */
    111    public static Charset toCharset(final String charsetName) {
    112        return charsetName == null ? Charset.defaultCharset() : Charset.forName(charsetName);
    113    }
    114
    115    /**
    116     * CharEncodingISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.
    117     * <p>
    118     * Every implementation of the Java platform is required to support this character encoding.
    119     * </p>
    120     *
    121     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    122     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    123     */
    124    @Deprecated
    125    public static final Charset ISO_8859_1 = StandardCharsets.ISO_8859_1;
    126
    127    /**
    128     * <p>
    129     * Seven-bit ASCII, also known as ISO646-US, also known as the Basic Latin block of the Unicode character set.
    130     * </p>
    131     * <p>
    132     * Every implementation of the Java platform is required to support this character encoding.
    133     * </p>
    134     *
    135     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    136     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    137     */
    138    @Deprecated
    139    public static final Charset US_ASCII = StandardCharsets.US_ASCII;
    140
    141    /**
    142     * <p>
    143     * Sixteen-bit Unicode Transformation Format, The byte order specified by a mandatory initial byte-order mark
    144     * (either order accepted on input, big-endian used on output)
    145     * </p>
    146     * <p>
    147     * Every implementation of the Java platform is required to support this character encoding.
    148     * </p>
    149     *
    150     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    151     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    152     */
    153    @Deprecated
    154    public static final Charset UTF_16 = StandardCharsets.UTF_16;
    155
    156    /**
    157     * <p>
    158     * Sixteen-bit Unicode Transformation Format, big-endian byte order.
    159     * </p>
    160     * <p>
    161     * Every implementation of the Java platform is required to support this character encoding.
    162     * </p>
    163     *
    164     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    165     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    166     */
    167    @Deprecated
    168    public static final Charset UTF_16BE = StandardCharsets.UTF_16BE;
    169
    170    /**
    171     * <p>
    172     * Sixteen-bit Unicode Transformation Format, little-endian byte order.
    173     * </p>
    174     * <p>
    175     * Every implementation of the Java platform is required to support this character encoding.
    176     * </p>
    177     *
    178     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    179     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    180     */
    181    @Deprecated
    182    public static final Charset UTF_16LE = StandardCharsets.UTF_16LE;
    183
    184    /**
    185     * <p>
    186     * Eight-bit Unicode Transformation Format.
    187     * </p>
    188     * <p>
    189     * Every implementation of the Java platform is required to support this character encoding.
    190     * </p>
    191     *
    192     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    193     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    194     */
    195    @Deprecated
    196    public static final Charset UTF_8 = StandardCharsets.UTF_8;
    197}