StringEncoderComparator.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 org.apache.commons.codec;

import java.util.Comparator;

/**
 * Compares Strings using a {@link StringEncoder}. This comparator is used to
 * sort Strings by an encoding scheme such as Soundex, Metaphone, etc. This
 * class can come in handy if one need to sort Strings by an encoded form of a
 * name such as Soundex.
 * 
 * <p>
 * This class is immutable and thread-safe.
 * </p>
 * 
 * @version $Id: StringEncoderComparator.java 1352268 2012-06-20 19:04:08Z
 *          ggregory $
 */
public class StringEncoderComparator implements Comparator {

	/**
	 * Internal encoder instance.
	 */
	private final StringEncoder stringEncoder;

	/**
	 * Constructs a new instance.
	 * 
	 * @deprecated Creating an instance without a {@link StringEncoder} leads to
	 *             a {@link NullPointerException}. Will be removed in 2.0.
	 */
	@Deprecated
	public StringEncoderComparator() {
		this.stringEncoder = null; // Trying to use this will cause things to
									// break
	}

	/**
	 * Constructs a new instance with the given algorithm.
	 * 
	 * @param stringEncoder
	 *            the StringEncoder used for comparisons.
	 */
	public StringEncoderComparator(StringEncoder stringEncoder) {
		this.stringEncoder = stringEncoder;
	}

	/**
	 * Compares two strings based not on the strings themselves, but on an
	 * encoding of the two strings using the StringEncoder this Comparator was
	 * created with.
	 * 
	 * If an {@link EncoderException} is encountered, return <code>0</code>.
	 * 
	 * @param o1
	 *            the object to compare
	 * @param o2
	 *            the object to compare to
	 * @return the Comparable.compareTo() return code or 0 if an encoding error
	 *         was caught.
	 * @see Comparable
	 */
	@Override
	public int compare(Object o1, Object o2) {

		int compareCode = 0;

		try {
			Comparable s1 = (Comparable) this.stringEncoder.encode(o1);
			Comparable s2 = (Comparable) this.stringEncoder.encode(o2);
			compareCode = s1.compareTo(s2);
		} catch (EncoderException ee) {
			compareCode = 0;
		}
		return compareCode;
	}

}