如何打印出集合{1,2,3,4,5,6}的所有子集？

package test;

import java.util.ArrayList;
import java.util.List;

public class Test {
	static int n =-1;
	public Test() {
		
	}
	public void print(List list)
	{
		for(int i=0;i<list.size();i++)
			System.out.print(list.get(i));
		System.out.println();
	}
	
	/*通过递归减少集合中元素的个数
	 * @index 控制排除递归出重复的结果
	 * @list 递归的List
	 */
	public List deal(int index,List list)
	{
		//把原List克隆
		List newList =(List) ((ArrayList)list).clone();
		
		print(list);
		n++;
		for(int i=0;i<list.size();i++)
		{
			if(i>=index)
			{
//				System.out.println("list大小:"+list.size());
//				System.out.println("index:"+index+"  i:"+i);
				list.remove(i);
				//递归调用
				deal(i,list);
				list = (List) ((ArrayList)newList).clone();
			}
		}
		return null;
	}
	public static void main(String[] args) {
		List list = new ArrayList();
		for(int i = 0 ; i < 5 ; i ++)
			list.add(new Integer(i));
		Test test = new Test();
		test.deal(0,list);
		System.out.println("@@@@@@@@@@@@@   "+n);
	}
}