LexicographicComparator.java

/*
 * Copyright (c) 2013, SRI International
 * All rights reserved.
 * Licensed under the The BSD 3-Clause License;
 * you may not use this file except in compliance with the License.
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 * 
 * http://opensource.org/licenses/BSD-3-Clause
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package com.sri.ai.util.collect;

import java.util.Arrays;
import java.util.Comparator;
import java.util.List;

import com.google.common.annotations.Beta;

/**
 * A comparator lexicographically composed by a list of comparators. The first
 * comparator in the list is used first and, if there is a tie, the next ones
 * are used successively.
 * 
 * @author braz
 */
@Beta
public class LexicographicComparator<T> implements Comparator<T> {
	
	private List<Comparator<T>> comparators;

	public LexicographicComparator(List<Comparator<T>> comparators) {
		this.comparators = comparators;
	}

	public LexicographicComparator(Comparator<T>... comparators) {
		this.comparators = Arrays.asList(comparators);
	}

	@Override
	public int compare(T o1, T o2) {
		return compare(o1, o2, 0);
	}

	private int compare(T o1, T o2, int i) {
		if (i == comparators.size()) {
			return 0;
		}
		Comparator<T> nextComparator = comparators.get(i);
		int resultForNextComparator = nextComparator.compare(o1, o2);
		if (resultForNextComparator == 0) {
			return compare(o1, o2, i+1);
		}
		return resultForNextComparator;
	}
}