多线程找出两个list之间不同的元素

突然之间，给自已想到了一题，找出两个list之间的不同元素。
尝试了用list循环 或 用hashSet 实现，但效率都太低了点。
如是尝试了一下用多线程去实验一下，效率大大提升 。。

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

/**
 * @author gah
 *
 * 2013-7-3
 */
public class CompareListThread {
	
	private List minList, maxList , retList;
	
	public CompareListThread(List list1, List list2) {
		if(list1.size() > list2.size()) {
			maxList = list1;
			minList = list2;
		} else {
			maxList = list2;
			minList = list1;
		}
		retList = new ArrayList();
	}
	
	private int getInterval() {
		return maxList.size()/10;
	}
	
	public void execute() throws Exception{
		int start, t;
        start = t = getInterval();
		ACT act = null;
		List<ACT> list = new ArrayList<ACT>();
		while(start < maxList.size()) {
			act = new ACT(start - t,start);
			start += t;
			act.start();
			list.add(act);
		}
		act = new ACT(start-t, maxList.size());
		act.start();
		list.add(act);
		for(ACT a:list) {
			a.join();
			retList.addAll(a.getResult());
		}
	}
	
	public List getResult() {
		return retList;
	}
	
	class ACT extends Thread {
		private List  rList;
		private int s, e;
		
		public ACT(int s, int e) {
			this.s = s; 
			this.e  = e;
			rList = new ArrayList();
		}
		
		@Override
		public void run() {
			Object o = null;
			for(;s < e; s++) {
				o = maxList.get(s);
				for(int i = 0,j=minList.size(); i < j; i++) {
					if(o == minList.get(i)) {
						o = null;
						break;
					}
				}
				if(null != o) {
					rList.add(o);
				}
			}
		}
		
		public List getResult() {
			return rList;
		}
		
	}

}

private static List compareSet(List list1, List list2) {
		long a = System.currentTimeMillis();
		List retList = new ArrayList();
		List minList;
		Set set = null;
		if(list1.size() > list2.size()) {
			set = new HashSet(list1);
			minList = list2;
		} else {
			set = new HashSet(list2);
			minList = list1;
		}
		set.removeAll(minList);
		System.out.println("compare2 method take time:" + (System.currentTimeMillis() - a));
		Iterator iter = set.iterator();
		while(iter.hasNext()) {
			retList.add(iter.next());
		}
		return retList;
	}

private static List compareList(List list1, List list2) {
		long a = System.currentTimeMillis();
		List retList = new ArrayList();
		List minList = list1 , maxList = list2;
		if(list1.size() > list2.size()) {
			maxList = list1;
			minList = list2;
		}
		for(int i = 0, count = maxList.size(); i < count; i++) {
			if(!minList.contains(maxList.get(i))) {
				retList.add(maxList.get(i));
			}
		}
		System.out.println("compare method take time:" + (System.currentTimeMillis() - a));
		return retList;
	}