StringUtils.java

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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.codec.binary;

import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;

import org.apache.commons.codec.CharEncoding;
import org.apache.commons.codec.Charsets;

/**
 * Converts String to and from bytes using the encodings required by the Java specification. These encodings are
 * specified in <a href="http://download.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">
 * Standard charsets</a>.
 *
 * <p>This class is immutable and thread-safe.</p>
 *
 * @see CharEncoding
 * @see <a href="http://download.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
 * @version $Id$
 * @since 1.4
 */
public class StringUtils {

    /**
     * Calls {@link String#getBytes(Charset)}
     *
     * @param string
     *            The string to encode (if null, return null).
     * @param charset
     *            The {@link Charset} to encode the {@code String}
     * @return the encoded bytes
     */
    private static byte[] getBytes(final String string, final Charset charset) {
        if (string == null) {
            return null;
        }
        return string.getBytes(charset);
    }

    /**
     * Encodes the given string into a sequence of bytes using the ISO-8859-1 charset, storing the result into a new
     * byte array.
     *
     * @param string
     *            the String to encode, may be {@code null}
     * @return encoded bytes, or {@code null} if the input string was {@code null}
     * @throws NullPointerException
     *             Thrown if {@link Charsets#ISO_8859_1} is not initialized, which should never happen since it is
     *             required by the Java platform specification.
     * @since As of 1.7, throws {@link NullPointerException} instead of UnsupportedEncodingException
     * @see <a href="http://download.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
     * @see #getBytesUnchecked(String, String)
     */
    public static byte[] getBytesIso8859_1(final String string) {
        return getBytes(string, Charsets.ISO_8859_1);
    }


    /**
     * Encodes the given string into a sequence of bytes using the named charset, storing the result into a new byte
     * array.
     * <p>
     * This method catches {@link UnsupportedEncodingException} and rethrows it as {@link IllegalStateException}, which
     * should never happen for a required charset name. Use this method when the encoding is required to be in the JRE.
     * </p>
     *
     * @param string
     *            the String to encode, may be {@code null}
     * @param charsetName
     *            The name of a required {@link java.nio.charset.Charset}
     * @return encoded bytes, or {@code null} if the input string was {@code null}
     * @throws IllegalStateException
     *             Thrown when a {@link UnsupportedEncodingException} is caught, which should never happen for a
     *             required charset name.
     * @see CharEncoding
     * @see String#getBytes(String)
     */
    public static byte[] getBytesUnchecked(final String string, final String charsetName) {
        if (string == null) {
            return null;
        }
        try {
            return string.getBytes(charsetName);
        } catch (final UnsupportedEncodingException e) {
            throw StringUtils.newIllegalStateException(charsetName, e);
        }
    }

    /**
     * Encodes the given string into a sequence of bytes using the US-ASCII charset, storing the result into a new byte
     * array.
     *
     * @param string
     *            the String to encode, may be {@code null}
     * @return encoded bytes, or {@code null} if the input string was {@code null}
     * @throws NullPointerException
     *             Thrown if {@link Charsets#US_ASCII} is not initialized, which should never happen since it is
     *             required by the Java platform specification.
     * @since As of 1.7, throws {@link NullPointerException} instead of UnsupportedEncodingException
     * @see <a href="http://download.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
     * @see #getBytesUnchecked(String, String)
     */
    public static byte[] getBytesUsAscii(final String string) {
        return getBytes(string, Charsets.US_ASCII);
    }

    /**
     * Encodes the given string into a sequence of bytes using the UTF-16 charset, storing the result into a new byte
     * array.
     *
     * @param string
     *            the String to encode, may be {@code null}
     * @return encoded bytes, or {@code null} if the input string was {@code null}
     * @throws NullPointerException
     *             Thrown if {@link Charsets#UTF_16} is not initialized, which should never happen since it is
     *             required by the Java platform specification.
     * @since As of 1.7, throws {@link NullPointerException} instead of UnsupportedEncodingException
     * @see <a href="http://download.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
     * @see #getBytesUnchecked(String, String)
     */
    public static byte[] getBytesUtf16(final String string) {
        return getBytes(string, Charsets.UTF_16);
    }

    /**
     * Encodes the given string into a sequence of bytes using the UTF-16BE charset, storing the result into a new byte
     * array.
     *
     * @param string
     *            the String to encode, may be {@code null}
     * @return encoded bytes, or {@code null} if the input string was {@code null}
     * @throws NullPointerException
     *             Thrown if {@link Charsets#UTF_16BE} is not initialized, which should never happen since it is
     *             required by the Java platform specification.
     * @since As of 1.7, throws {@link NullPointerException} instead of UnsupportedEncodingException
     * @see <a href="http://download.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
     * @see #getBytesUnchecked(String, String)
     */
    public static byte[] getBytesUtf16Be(final String string) {
        return getBytes(string, Charsets.UTF_16BE);
    }

    /**
     * Encodes the given string into a sequence of bytes using the UTF-16LE charset, storing the result into a new byte
     * array.
     *
     * @param string
     *            the String to encode, may be {@code null}
     * @return encoded bytes, or {@code null} if the input string was {@code null}
     * @throws NullPointerException
     *             Thrown if {@link Charsets#UTF_16LE} is not initialized, which should never happen since it is
     *             required by the Java platform specification.
     * @since As of 1.7, throws {@link NullPointerException} instead of UnsupportedEncodingException
     * @see <a href="http://download.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
     * @see #getBytesUnchecked(String, String)
     */
    public static byte[] getBytesUtf16Le(final String string) {
        return getBytes(string, Charsets.UTF_16LE);
    }

    /**
     * Encodes the given string into a sequence of bytes using the UTF-8 charset, storing the result into a new byte
     * array.
     *
     * @param string
     *            the String to encode, may be {@code null}
     * @return encoded bytes, or {@code null} if the input string was {@code null}
     * @throws NullPointerException
     *             Thrown if {@link Charsets#UTF_8} is not initialized, which should never happen since it is
     *             required by the Java platform specification.
     * @since As of 1.7, throws {@link NullPointerException} instead of UnsupportedEncodingException
     * @see <a href="http://download.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
     * @see #getBytesUnchecked(String, String)
     */
    public static byte[] getBytesUtf8(final String string) {
        return getBytes(string, Charsets.UTF_8);
    }

    private static IllegalStateException newIllegalStateException(final String charsetName,
                                                                  final UnsupportedEncodingException e) {
        return new IllegalStateException(charsetName + ": " + e);
    }

    /**
     * Constructs a new <code>String</code> by decoding the specified array of bytes using the given charset.
     *
     * @param bytes
     *            The bytes to be decoded into characters
     * @param charset
     *            The {@link Charset} to encode the {@code String}
     * @return A new <code>String</code> decoded from the specified array of bytes using the given charset,
     *         or {@code null} if the input byte array was {@code null}.
     * @throws NullPointerException
     *             Thrown if {@link Charsets#UTF_8} is not initialized, which should never happen since it is
     *             required by the Java platform specification.
     */
    private static String newString(final byte[] bytes, final Charset charset) {
        return bytes == null ? null : new String(bytes, charset);
    }

    /**
     * Constructs a new <code>String</code> by decoding the specified array of bytes using the given charset.
     * <p>
     * This method catches {@link UnsupportedEncodingException} and re-throws it as {@link IllegalStateException}, which
     * should never happen for a required charset name. Use this method when the encoding is required to be in the JRE.
     * </p>
     *
     * @param bytes
     *            The bytes to be decoded into characters, may be {@code null}
     * @param charsetName
     *            The name of a required {@link java.nio.charset.Charset}
     * @return A new <code>String</code> decoded from the specified array of bytes using the given charset,
     *         or {@code null} if the input byte array was {@code null}.
     * @throws IllegalStateException
     *             Thrown when a {@link UnsupportedEncodingException} is caught, which should never happen for a
     *             required charset name.
     * @see CharEncoding
     * @see String#String(byte[], String)
     */
    public static String newString(final byte[] bytes, final String charsetName) {
        if (bytes == null) {
            return null;
        }
        try {
            return new String(bytes, charsetName);
        } catch (final UnsupportedEncodingException e) {
            throw StringUtils.newIllegalStateException(charsetName, e);
        }
    }

    /**
     * Constructs a new <code>String</code> by decoding the specified array of bytes using the ISO-8859-1 charset.
     *
     * @param bytes
     *            The bytes to be decoded into characters, may be {@code null}
     * @return A new <code>String</code> decoded from the specified array of bytes using the ISO-8859-1 charset, or
     *         {@code null} if the input byte array was {@code null}.
     * @throws NullPointerException
     *             Thrown if {@link Charsets#ISO_8859_1} is not initialized, which should never happen since it is
     *             required by the Java platform specification.
     * @since As of 1.7, throws {@link NullPointerException} instead of UnsupportedEncodingException
     */
    public static String newStringIso8859_1(final byte[] bytes) {
        return new String(bytes, Charsets.ISO_8859_1);
    }

    /**
     * Constructs a new <code>String</code> by decoding the specified array of bytes using the US-ASCII charset.
     *
     * @param bytes
     *            The bytes to be decoded into characters
     * @return A new <code>String</code> decoded from the specified array of bytes using the US-ASCII charset,
     *         or {@code null} if the input byte array was {@code null}.
     * @throws NullPointerException
     *             Thrown if {@link Charsets#US_ASCII} is not initialized, which should never happen since it is
     *             required by the Java platform specification.
     * @since As of 1.7, throws {@link NullPointerException} instead of UnsupportedEncodingException
     */
    public static String newStringUsAscii(final byte[] bytes) {
        return new String(bytes, Charsets.US_ASCII);
    }

    /**
     * Constructs a new <code>String</code> by decoding the specified array of bytes using the UTF-16 charset.
     *
     * @param bytes
     *            The bytes to be decoded into characters
     * @return A new <code>String</code> decoded from the specified array of bytes using the UTF-16 charset
     *         or {@code null} if the input byte array was {@code null}.
     * @throws NullPointerException
     *             Thrown if {@link Charsets#UTF_16} is not initialized, which should never happen since it is
     *             required by the Java platform specification.
     * @since As of 1.7, throws {@link NullPointerException} instead of UnsupportedEncodingException
     */
    public static String newStringUtf16(final byte[] bytes) {
        return new String(bytes, Charsets.UTF_16);
    }

    /**
     * Constructs a new <code>String</code> by decoding the specified array of bytes using the UTF-16BE charset.
     *
     * @param bytes
     *            The bytes to be decoded into characters
     * @return A new <code>String</code> decoded from the specified array of bytes using the UTF-16BE charset,
     *         or {@code null} if the input byte array was {@code null}.
     * @throws NullPointerException
     *             Thrown if {@link Charsets#UTF_16BE} is not initialized, which should never happen since it is
     *             required by the Java platform specification.
     * @since As of 1.7, throws {@link NullPointerException} instead of UnsupportedEncodingException
     */
    public static String newStringUtf16Be(final byte[] bytes) {
        return new String(bytes, Charsets.UTF_16BE);
    }

    /**
     * Constructs a new <code>String</code> by decoding the specified array of bytes using the UTF-16LE charset.
     *
     * @param bytes
     *            The bytes to be decoded into characters
     * @return A new <code>String</code> decoded from the specified array of bytes using the UTF-16LE charset,
     *         or {@code null} if the input byte array was {@code null}.
     * @throws NullPointerException
     *             Thrown if {@link Charsets#UTF_16LE} is not initialized, which should never happen since it is
     *             required by the Java platform specification.
     * @since As of 1.7, throws {@link NullPointerException} instead of UnsupportedEncodingException
     */
    public static String newStringUtf16Le(final byte[] bytes) {
        return new String(bytes, Charsets.UTF_16LE);
    }

    /**
     * Constructs a new <code>String</code> by decoding the specified array of bytes using the UTF-8 charset.
     *
     * @param bytes
     *            The bytes to be decoded into characters
     * @return A new <code>String</code> decoded from the specified array of bytes using the UTF-8 charset,
     *         or {@code null} if the input byte array was {@code null}.
     * @throws NullPointerException
     *             Thrown if {@link Charsets#UTF_8} is not initialized, which should never happen since it is
     *             required by the Java platform specification.
     * @since As of 1.7, throws {@link NullPointerException} instead of UnsupportedEncodingException
     */
    public static String newStringUtf8(final byte[] bytes) {
        return newString(bytes, Charsets.UTF_8);
    }

}