org.eclipse.viatra2.core2/src/org/eclipse/viatra2/core/simple/CollectionsDisjunktTester.java

/*******************************************************************************
 * Copyright (c) 2004-2008 Andras Schmidt, Andras Balogh, Istvan Rath and Daniel Varro
 * 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:
 *    Andras Schmidt, Andras Balogh, Istvan Rath - initial API and implementation
 *******************************************************************************/

package org.eclipse.viatra2.core.simple;

import java.util.Collection;
import java.util.Iterator;
import java.util.TreeSet;

/**
 * This class implements an algorithm to test two collections whether they are
 * disjunkt or not.
 * 
 * @author Andras Schmidt
 * 
 */
public class CollectionsDisjunktTester {
	/**
	 * Tests whether the two collections are disjunkt or not. Will work fast
	 * (TODO) if ordered sets are given (with the same ordering).
	 * 
	 * @param col1
	 * @param col2
	 * @return
	 */
	public static boolean isDisjunct(Collection col1, Collection col2) {
		// TODO try to find out the structure of collections and implement a
		// faster search
		return isDisjunctBruteForce(col1, col2);
	}

	private static boolean isDisjunctBruteForce(Collection col1, Collection col2) {
		Iterator it = col1.iterator();
		while (it.hasNext()) {
			if (col2.contains(it.next()))
				return false;
		}
		return true;
	}

	/**
	 * returns the shared objects in the two collections. Will work fast (TODO)
	 * if ordered sets are given (with the same ordering).
	 * 
	 * @param col1
	 * @param col2
	 * @return
	 */
	public static Collection<Object> sharedElements(Collection col1,
			Collection col2) {
		TreeSet<Object> ret = new TreeSet<Object>();
		Iterator it = col1.iterator();
		while (it.hasNext()) {
			Object o = it.next();
			if (col2.contains(o))
				ret.add(o);
		}
		return ret;
	}
}