java集合运算：求交集，并集，集合差

import java.util.HashSet;
import java.util.Set;

public class Test {
	public static void main(String[] args) {
		Set<Integer> result = new HashSet<Integer>();
		
		Set<Integer> set1 = new HashSet<Integer>();
		
		Set<Integer> set2 = new HashSet<Integer>();
		
		set1.add(11);
		set1.add(22);
		set1.add(333);
		set1.add(4);
		
		set2.add(22);
		set2.add(333);
		set2.add(1);
		
		System.out.println("set1 = "+set1.toString());
		System.out.println("set2 = "+set2.toString());
		
		result.clear();
		result.addAll(set1);
		result.retainAll(set2);
		System.out.println("交集 = " + result);
		
		result.clear();
		result.addAll(set1);
		result.removeAll(set2);
		System.out.println("差集 = "+result);
		
		result.clear();
		result.addAll(set1);
		result.addAll(set2);
		System.out.println("并集 = " + result);
	}
}