org.jdal.util.comparator.AlphaNumericComparator.java Source code

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Here is the source code for org.jdal.util.comparator.AlphaNumericComparator.java

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/*
 * Copyright 2009-2011 the original author or authors.
 *
 * Licensed 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.jdal.util.comparator;

import java.util.Comparator;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * An alhpa numeric comparator. ie 10 is after 9.
 * 
 * @author Jose Luis Martin.
 * @since 1.0
 */
public class AlphaNumericComparator implements Comparator<String> {

    private static final Log log = LogFactory.getLog(AlphaNumericComparator.class);

    /**
     * {@inheritDoc}
     */
    public int compare(String o1, String o2) {
        try {
            Pattern pattern = Pattern.compile("([0-9]+)");
            Matcher matcher1 = pattern.matcher(o1);
            Matcher matcher2 = pattern.matcher(o2);

            if ((matcher1.find() && matcher2.find()) && o1.startsWith(o2.substring(0, matcher2.start()))) {
                // two strings have numbers, and same prefix.
                // use numeric comparation
                Integer n1 = Integer.valueOf(matcher1.group());
                Integer n2 = Integer.valueOf(matcher2.group());
                return n1.compareTo(n2);
            }
            // else return string comparation
            return o1.compareToIgnoreCase(o2);
        } catch (Exception e) {
            log.error(e);
        }
        return 0; // On Exception object are equals
    }

}