StringUtils.java

/*
 * 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 io.multibase.binary;

import io.multibase.CharEncoding;
import io.multibase.Charsets;
import java.nio.charset.Charset;

/**
 * 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/7/docs/api/java/nio/charset/Charset.html">Standard
 * charsets</a>.
 *
 * <p>This class is immutable and thread-safe.
 *
 * @see CharEncoding
 * @see <a
 *     href="http://download.oracle.com/javase/7/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</code>
   * @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 UTF-8 charset, storing the result
   * into a new byte array.
   *
   * @param string the String to encode, may be <code>null</code>
   * @return encoded bytes, or <code>null</code> if the input string was <code>null</code>
   * @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/7/docs/api/java/nio/charset/Charset.html">Standard
   *     charsets</a>
   */
  public static byte[] getBytesUtf8(final String string) {
    return getBytes(string, Charset.forName("UTF-8"));
  }

  /**
   * 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</code>; not {@code null}
   * @return A new <code>String</code> decoded from the specified array of bytes using the given
   *     charset, or <code>null</code> if the input byte array was <code>null</code>.
   * @throws NullPointerException Thrown if charset is {@code null}
   */
  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
   * 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</code> if the input byte array was <code>null</code>.
   * @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 newString(bytes, Charset.forName("US-ASCII"));
  }

  /**
   * 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</code> if the input byte array was <code>null</code>.
   * @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, Charset.forName("UTF-8"));
  }
}