Java tutorial
/* * 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); } }