SetUtils.java

//The MIT License
//
// Copyright (c) 2004 Mindswap Research Group, University of Maryland, College Park
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.

package org.mindswap.swoop.utils;

import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

/**
 * @author Evren Sirin
 */
public class SetUtils {
	/**
	 * Returns the union of all the sets given in a collection. 
	 * 
	 * @param coll A Collection of sets
	 */
	public static Set union(Collection coll) {
		Set set = new HashSet();
		for(Iterator i = coll.iterator(); i.hasNext(); ) {
			set.addAll((Collection) i.next());
		}
		
		return set;
	}
	
	/**
	 * Returns the union of two collections 
	 * 
	 * @param coll A Collection of sets
	 */
	public static Set union(Collection c1, Collection c2) {
		Set set = new HashSet();
		set.addAll(c1);
		set.addAll(c2);
		
		return set;
	}	

	/**
	 * Returns the intersection of two collections 
	 * 
	 * @param coll A Collection of sets
	 */
	public static Set intersection(Collection c1, Collection c2) {
		Set set = new HashSet();
		set.addAll(c1);
		set.retainAll(c2);
		
		return set;
	}	
	
	/**
	 * Checks if two collections have any elemnts in common 
	 * 
	 * @param coll A Collection of sets
	 */
	public static boolean intersects(Collection c1, Collection c2) {
		for(Iterator i = c1.iterator(); i.hasNext(); ) {
			if(c2.contains(i.next()))
				return true;
		}
		
		return false;
	}		

	/**
	 * Checks if one set is subset of another one
	 * 
	 * @param sub
	 * @param sup
	 * @return
	 */
	public static boolean subset(Set sub, Set sup) {
		for(Iterator i = sub.iterator(); i.hasNext(); ) {
			if(!sup.contains(i.next()))
				return false;
		}
		
		return true;
	}
	
	/**
	 * Returns the difference of two sets. All the elements of second set is
	 * removed from the first set  
	 * 
	 * @param coll A Collection of sets
	 */
	public static Set difference(Collection c1, Collection c2) {
		Set set = new HashSet();
		set.addAll(c1);
		set.removeAll(c2);
		
		return set;
	}		
	
	/**
	 * 
	 * Creates a list containing all the elements in the array
	 * 
	 * @param elements
	 * @return
	 */
	public static Set create(Object[] elems) {
		Set set = new HashSet();
		for(int i = 0; i < elems.length; i++)
			set.add(elems[i]);
		
		return set;
	}
	
	
	/**
	 * 
	 * Creates a set containing all the elements in the collection
	 * 
	 * @param elements
	 * @return
	 */
	public static Set create(Collection coll) {
		return new HashSet(coll);
	}	
}