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Apache Commons Compress software defines an API for working with compression and archive formats. These include: bzip2, gzip, pack200, lzma, xz, Snappy, traditional Unix Compress, DEFLATE, DEFLATE64, LZ4, Brotli, Zstandard and ar, cpio, jar, tar, zip, dump, 7z, arj.
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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 */

package org.apache.commons.compress.utils;

import java.nio.charset.Charset;
import java.nio.charset.UnsupportedCharsetException;

/**
 * Charsets required of every implementation of the Java platform.
 * 
 * From the Java documentation Standard
 * charsets:
 * 
 * Every implementation of the Java platform is required to support the following character encodings. Consult the
 * release documentation for your implementation to see if any other encodings are supported. Consult the release
 * documentation for your implementation to see if any other encodings are supported. 
 * 
 * 
 * 
 * US-ASCII

 * Seven-bit ASCII, a.k.a. ISO646-US, a.k.a. the Basic Latin block of the Unicode character set.
 * ISO-8859-1

 * ISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.
 * UTF-8

 * Eight-bit Unicode Transformation Format.
 * UTF-16BE

 * Sixteen-bit Unicode Transformation Format, big-endian byte order.
 * UTF-16LE

 * Sixteen-bit Unicode Transformation Format, little-endian byte order.
 * UTF-16

 * Sixteen-bit Unicode Transformation Format, byte order specified by a mandatory initial byte-order mark (either order
 * accepted on input, big-endian used on output.)
 * 
 * 
 * This class best belongs in the Commons Lang or IO project. Even if a similar class is defined in another Commons component, it is
 * not foreseen that Commons Compress would be made to depend on another Commons component.
 * 
 * @see Standard charsets
 * @since 1.4
 * @version $Id: Charsets.java 1309643 2012-04-05 04:01:32Z ggregory $
 */
public class Charsets {
    
    //
    // This class should only contain Charset instances for required encodings. This guarantees that it will load correctly and
    // without delay on all Java platforms.
    //
    
    /**
     * Returns the given Charset or the default Charset if the given Charset is null. 
     * 
     * @param charset
     *            A charset or null.
     * @return the given Charset or the default Charset if the given Charset is null
     */
    public static Charset toCharset(Charset charset) {
        return charset == null ? Charset.defaultCharset() : charset;
    }

    /**
     * Returns a Charset for the named charset. If the name is null, return the default Charset.
     * 
     * @param charset
     *            The name of the requested charset, may be null.
     * @return a Charset for the named charset
     * @throws UnsupportedCharsetException
     *             If the named charset is unavailable
     */
    public static Charset toCharset(String charset) {
        return charset == null ? Charset.defaultCharset() : Charset.forName(charset);
    }

    /**
     * CharsetNamesISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1. 
     * 
     * Every implementation of the Java platform is required to support this character encoding.
     * 
     * 
     * @see Standard charsets
     */
    public static final Charset ISO_8859_1 = Charset.forName(CharsetNames.ISO_8859_1);

    /**
     * 
     * Seven-bit ASCII, also known as ISO646-US, also known as the Basic Latin block of the Unicode character set.
     * 
     * 
     * Every implementation of the Java platform is required to support this character encoding.
     * 
     * 
     * @see Standard charsets
     */
    public static final Charset US_ASCII = Charset.forName(CharsetNames.US_ASCII);

    /**
     * 
     * Sixteen-bit Unicode Transformation Format, The byte order specified by a mandatory initial byte-order mark
     * (either order accepted on input, big-endian used on output)
     * 
     * 
     * Every implementation of the Java platform is required to support this character encoding.
     * 
     * 
     * @see Standard charsets
     */
    public static final Charset UTF_16 = Charset.forName(CharsetNames.UTF_16);

    /**
     * 
     * Sixteen-bit Unicode Transformation Format, big-endian byte order.
     * 
     * 
     * Every implementation of the Java platform is required to support this character encoding.
     * 
     * 
     * @see Standard charsets
     */
    public static final Charset UTF_16BE = Charset.forName(CharsetNames.UTF_16BE);

    /**
     * 
     * Sixteen-bit Unicode Transformation Format, little-endian byte order.
     * 
     * 
     * Every implementation of the Java platform is required to support this character encoding.
     * 
     * 
     * @see Standard charsets
     */
    public static final Charset UTF_16LE = Charset.forName(CharsetNames.UTF_16LE);

    /**
     * 
     * Eight-bit Unicode Transformation Format.
     * 
     * 
     * Every implementation of the Java platform is required to support this character encoding.
     * 
     * 
     * @see Standard charsets
     */
    public static final Charset UTF_8 = Charset.forName(CharsetNames.UTF_8);
}