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/8/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/8/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     * CharEncodingISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.
078     * <p>
079     * Every implementation of the Java platform is required to support this character encoding.
080     * </p>
081     *
082     * @see <a href="https://docs.oracle.com/javase/8/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
083     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
084     */
085    @Deprecated
086    public static final Charset ISO_8859_1 = StandardCharsets.ISO_8859_1;
087
088    /**
089     * <p>
090     * Seven-bit ASCII, also known as ISO646-US, also known as the Basic Latin block of the Unicode character set.
091     * </p>
092     * <p>
093     * Every implementation of the Java platform is required to support this character encoding.
094     * </p>
095     *
096     * @see <a href="https://docs.oracle.com/javase/8/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
097     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
098     */
099    @Deprecated
100    public static final Charset US_ASCII = StandardCharsets.US_ASCII;
101
102    /**
103     * <p>
104     * Sixteen-bit Unicode Transformation Format, The byte order specified by a mandatory initial byte-order mark
105     * (either order accepted on input, big-endian used on output)
106     * </p>
107     * <p>
108     * Every implementation of the Java platform is required to support this character encoding.
109     * </p>
110     *
111     * @see <a href="https://docs.oracle.com/javase/8/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
112     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
113     */
114    @Deprecated
115    public static final Charset UTF_16 = StandardCharsets.UTF_16;
116
117    /**
118     * <p>
119     * Sixteen-bit Unicode Transformation Format, big-endian byte order.
120     * </p>
121     * <p>
122     * Every implementation of the Java platform is required to support this character encoding.
123     * </p>
124     *
125     * @see <a href="https://docs.oracle.com/javase/8/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
126     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
127     */
128    @Deprecated
129    public static final Charset UTF_16BE = StandardCharsets.UTF_16BE;
130
131    /**
132     * <p>
133     * Sixteen-bit Unicode Transformation Format, little-endian byte order.
134     * </p>
135     * <p>
136     * Every implementation of the Java platform is required to support this character encoding.
137     * </p>
138     *
139     * @see <a href="https://docs.oracle.com/javase/8/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
140     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
141     */
142    @Deprecated
143    public static final Charset UTF_16LE = StandardCharsets.UTF_16LE;
144
145    /**
146     * <p>
147     * Eight-bit Unicode Transformation Format.
148     * </p>
149     * <p>
150     * Every implementation of the Java platform is required to support this character encoding.
151     * </p>
152     *
153     * @see <a href="https://docs.oracle.com/javase/8/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
154     * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
155     */
156    @Deprecated
157    public static final Charset UTF_8 = StandardCharsets.UTF_8;
158
159    /**
160     * Constructs a sorted map from canonical charset names to charset objects required of every implementation of the
161     * Java platform.
162     * <p>
163     * From the Java documentation <a href="https://docs.oracle.com/javase/8/docs/api/java/nio/charset/Charset.html">
164     * Standard charsets</a>:
165     * </p>
166     *
167     * @return An immutable, case-insensitive map from canonical charset names to charset objects.
168     * @see Charset#availableCharsets()
169     * @since 2.5
170     */
171    public static SortedMap<String, Charset> requiredCharsets() {
172        return STANDARD_CHARSET_MAP;
173    }
174
175    /**
176     * Returns the given Charset or the default Charset if the given Charset is null.
177     *
178     * @param charset
179     *            A charset or null.
180     * @return the given Charset or the default Charset if the given Charset is null
181     */
182    public static Charset toCharset(final Charset charset) {
183        return charset == null ? Charset.defaultCharset() : charset;
184    }
185
186    /**
187     * Returns the given charset if non-null, otherwise return defaultCharset.
188     *
189     * @param charset The charset to test, may be null.
190     * @param defaultCharset The charset to return if charset is null, may be null.
191     * @return a Charset .
192     * @since 2.12.0
193     */
194    public static Charset toCharset(final Charset charset, final Charset defaultCharset) {
195        return charset == null ? defaultCharset : charset;
196    }
197
198    /**
199     * Returns a Charset for the named charset. If the name is null, return the default Charset.
200     *
201     * @param charsetName The name of the requested charset, may be null.
202     * @return a Charset for the named charset.
203     * @throws UnsupportedCharsetException If the named charset is unavailable (unchecked exception).
204     */
205    public static Charset toCharset(final String charsetName) throws UnsupportedCharsetException {
206        return toCharset(charsetName, Charset.defaultCharset());
207    }
208
209    /**
210     * Returns a Charset for the named charset. If the name is null, return the given default Charset.
211     *
212     * @param charsetName The name of the requested charset, may be null.
213     * @param defaultCharset The name charset to return if charsetName is null, may be null.
214     * @return a Charset for the named charset.
215     * @throws UnsupportedCharsetException If the named charset is unavailable (unchecked exception).
216     * @since 2.12.0
217     */
218    public static Charset toCharset(final String charsetName, final Charset defaultCharset) throws UnsupportedCharsetException {
219        return charsetName == null ? defaultCharset : Charset.forName(charsetName);
220    }
221}