NumberAwareComparableComparator.java

/*
 * Copyright 2004-2005 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.springmodules.validation.util.condition.range;

import java.math.BigDecimal;
import java.security.InvalidParameterException;

import org.springframework.util.comparator.ComparableComparator;

/**
 * A comparator that compares {@link Comparable} instances but treats comparison
 * of {@link Number} instances in a special manner. In order to support
 * comparison of numbers regardless of their type, this comparator transform the
 * numbers to {@link BigDecimal} and then does the comparison.
 * 
 * @author Uri Boness
 */
public class NumberAwareComparableComparator extends ComparableComparator
{

	/**
	 * Compares the two given objects. Expects both of them to be
	 * {@link Comparable} instances.
	 * 
	 * @see ComparableComparator#compare(Object, Object)
	 */
	public int compare(Object o1, Object o2)
	{
		if (Number.class.isInstance(o1) && Number.class.isInstance(o2))
		{
			return compareNumbers((Number) o1, (Number) o2);
		}

		throw new InvalidParameterException("Object must be of type number");
	}

	/**
	 * Compares the two given numbers. These numbers are compared regardless of
	 * their type.
	 * 
	 * @param n1
	 *            The first number.
	 * @param n2
	 *            The second number.
	 * @return possitive number if <code>n1 > n2</code>, negative number if
	 *         <code>n1 < n2</code>, or 0 (Zero) if <code>n1 == n2</code>.
	 */
	protected int compareNumbers(Number n1, Number n2)
	{
		BigDecimal bd1 = new BigDecimal(n1.toString());
		BigDecimal bd2 = new BigDecimal(n2.toString());
		return bd1.compareTo(bd2);
	}

}