    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.nio.charset.UnsupportedCharsetException;
    022import java.util.Collections;
    023import java.util.SortedMap;
    024import java.util.TreeMap;
    025
    026/**
    027 * Charsets required of every implementation of the Java platform.
    028 *
    029 * From the Java documentation <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">
    030 * Standard charsets</a>:
    031 * <p>
    032 * <cite>Every implementation of the Java platform is required to support the following character encodings. Consult
    033 * the release documentation for your implementation to see if any other encodings are supported. Consult the release
    034 * documentation for your implementation to see if any other encodings are supported. </cite>
    035 * </p>
    036 *
    037 * <ul>
    038 * <li>{@code US-ASCII}<br>
    039 * Seven-bit ASCII, a.k.a. ISO646-US, a.k.a. the Basic Latin block of the Unicode character set.</li>
    040 * <li>{@code ISO-8859-1}<br>
    041 * ISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.</li>
    042 * <li>{@code UTF-8}<br>
    043 * Eight-bit Unicode Transformation Format.</li>
    044 * <li>{@code UTF-16BE}<br>
    045 * Sixteen-bit Unicode Transformation Format, big-endian byte order.</li>
    046 * <li>{@code UTF-16LE}<br>
    047 * Sixteen-bit Unicode Transformation Format, little-endian byte order.</li>
    048 * <li>{@code UTF-16}<br>
    049 * Sixteen-bit Unicode Transformation Format, byte order specified by a mandatory initial byte-order mark (either order
    050 * accepted on input, big-endian used on output.)</li>
    051 * </ul>
    052 *
    053 * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    054 * @since 2.3
    055 */
    056public class Charsets {
    057
    058    //
    059    // This class should only contain Charset instances for required encodings. This guarantees that it will load
    060    // correctly and without delay on all Java platforms.
    061    //
    062
    063    private static final SortedMap<String, Charset> STANDARD_CHARSET_MAP;
    064
    065    static {
    066        final SortedMap<String, Charset> standardCharsetMap = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
    067        standardCharsetMap.put(StandardCharsets.ISO_8859_1.name(), StandardCharsets.ISO_8859_1);
    068        standardCharsetMap.put(StandardCharsets.US_ASCII.name(), StandardCharsets.US_ASCII);
    069        standardCharsetMap.put(StandardCharsets.UTF_16.name(), StandardCharsets.UTF_16);
    070        standardCharsetMap.put(StandardCharsets.UTF_16BE.name(), StandardCharsets.UTF_16BE);
    071        standardCharsetMap.put(StandardCharsets.UTF_16LE.name(), StandardCharsets.UTF_16LE);
    072        standardCharsetMap.put(StandardCharsets.UTF_8.name(), StandardCharsets.UTF_8);
    073        STANDARD_CHARSET_MAP = Collections.unmodifiableSortedMap(standardCharsetMap);
    074    }
    075
    076    /**
    077     * Constructs a sorted map from canonical charset names to charset objects required of every implementation of the
    078     * Java platform.
    079     * <p>
    080     * From the Java documentation <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">
    081     * Standard charsets</a>:
    082     * </p>
    083     *
    084     * @return An immutable, case-insensitive map from canonical charset names to charset objects.
    085     * @see Charset#availableCharsets()
    086     * @since 2.5
    087     */
    088    public static SortedMap<String, Charset> requiredCharsets() {
    089        return STANDARD_CHARSET_MAP;
    090    }
    091
    092    /**
    093     * Returns the given Charset or the default Charset if the given Charset is null.
    094     *
    095     * @param charset
    096     *            A charset or null.
    097     * @return the given Charset or the default Charset if the given Charset is null
    098     */
    099    public static Charset toCharset(final Charset charset) {
    100        return charset == null ? Charset.defaultCharset() : charset;
    101    }
    102
    103    /**
    104     * Returns a Charset for the named charset. If the name is null, return the default Charset.
    105     *
    106     * @param charsetName The name of the requested charset, may be null.
    107     * @return a Charset for the named charset.
    108     * @throws UnsupportedCharsetException If the named charset is unavailable (unchecked exception).
    109     */
    110    public static Charset toCharset(final String charsetName) throws UnsupportedCharsetException {
    111        return charsetName == null ? Charset.defaultCharset() : Charset.forName(charsetName);
    112    }
    113
    114    /**
    115     * CharEncodingISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.
    116     * <p>
    117     * Every implementation of the Java platform is required to support this character encoding.
    118     * </p>
    119     *
    120     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    121     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    122     */
    123    @Deprecated
    124    public static final Charset ISO_8859_1 = StandardCharsets.ISO_8859_1;
    125
    126    /**
    127     * <p>
    128     * Seven-bit ASCII, also known as ISO646-US, also known as the Basic Latin block of the Unicode character set.
    129     * </p>
    130     * <p>
    131     * Every implementation of the Java platform is required to support this character encoding.
    132     * </p>
    133     *
    134     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    135     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    136     */
    137    @Deprecated
    138    public static final Charset US_ASCII = StandardCharsets.US_ASCII;
    139
    140    /**
    141     * <p>
    142     * Sixteen-bit Unicode Transformation Format, The byte order specified by a mandatory initial byte-order mark
    143     * (either order accepted on input, big-endian used on output)
    144     * </p>
    145     * <p>
    146     * Every implementation of the Java platform is required to support this character encoding.
    147     * </p>
    148     *
    149     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    150     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    151     */
    152    @Deprecated
    153    public static final Charset UTF_16 = StandardCharsets.UTF_16;
    154
    155    /**
    156     * <p>
    157     * Sixteen-bit Unicode Transformation Format, big-endian byte order.
    158     * </p>
    159     * <p>
    160     * Every implementation of the Java platform is required to support this character encoding.
    161     * </p>
    162     *
    163     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    164     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    165     */
    166    @Deprecated
    167    public static final Charset UTF_16BE = StandardCharsets.UTF_16BE;
    168
    169    /**
    170     * <p>
    171     * Sixteen-bit Unicode Transformation Format, little-endian byte order.
    172     * </p>
    173     * <p>
    174     * Every implementation of the Java platform is required to support this character encoding.
    175     * </p>
    176     *
    177     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    178     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    179     */
    180    @Deprecated
    181    public static final Charset UTF_16LE = StandardCharsets.UTF_16LE;
    182
    183    /**
    184     * <p>
    185     * Eight-bit Unicode Transformation Format.
    186     * </p>
    187     * <p>
    188     * Every implementation of the Java platform is required to support this character encoding.
    189     * </p>
    190     *
    191     * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    192     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
    193     */
    194    @Deprecated
    195    public static final Charset UTF_8 = StandardCharsets.UTF_8;
    196}