/*******************************************************************************
* Copyright (c) 2002 - 2006 IBM Corporation.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package com.ibm.wala.util.collections;
import java.util.Comparator;
/**
* A comparator based on hash codes
*/
public class HashCodeComparator<T> implements Comparator<T> {
@SuppressWarnings("rawtypes")
private static final HashCodeComparator INSTANCE = new HashCodeComparator();
/*
* @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
*/
@Override
public int compare(T o1, T o2) throws NullPointerException {
// by convention null is less than non-null
if (o1 == null) {
return o2 == null ? 0 : -1;
} else if (o2 == null) {
return 1;
}
return o1.hashCode() - o2.hashCode();
}
@SuppressWarnings("unchecked")
public static <T> HashCodeComparator<T> instance() {
return INSTANCE;
}
}