两个集合求交集

package aasdfsa;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Random;
import java.util.Set;

import org.apache.commons.collections.Bag;
import org.apache.commons.collections.bag.HashBag;

public class TwoArrayList {
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		TwoArrayList t = new TwoArrayList();
		
		List<String> one = new ArrayList<String>();
		List<String> two = new ArrayList<String>();
		long now = System.currentTimeMillis();
		int bigtime = 1000;//运行时间
		Random r = new Random();
		int key = 100000;//取值范围
		for(;;){
			int rr = r.nextInt(key);
			one.add(""+rr);
			rr = r.nextInt(1000);
			if(r.nextBoolean())two.add(""+rr);
		
			if(now+bigtime < System.currentTimeMillis()){
				break;
			}
		}
		System.out.println("first:"+one.size());
		System.out.println("next:"+two.size());
		System.out.println("union:"+t.union(one,two).size());

	}
	public List<String> union(List<String> one ,List<String> two){
		Bag bag1 = new HashBag(one);
		Bag bag2 = new HashBag(two);
		Set<String> set = new HashSet<String>();
		List<String> result = new ArrayList<String>();		
		set.addAll(one);
		set.addAll(two);
		System.out.println("totle:"+set.size());
		for (String temp : set) {
			long first = bag1.getCount(temp);
			long secend = bag2.getCount(temp);
			for(int i = 0 ; i < Math.min(first, secend);i++){
				result.add(temp);
			}			
		}
		return result;
	}

}

评论

3 楼 <>++< 2011-10-18  

		public static List<String> listA = new ArrayList<String>(Arrays.asList("a",
				"b", "c", "c", "d"));
		public static List<String> listB = new ArrayList<String>(Arrays.asList("d",
				"b", "c", "c", "d"));
		
		listA = new ArrayList<String>(new HashSet<String>(listA));
		listA.retainAll(listB);

		for (String str : listA) {
			System.out.println(str);
		}

LZ 是这意思么？

2 楼 抛出异常的爱 2010-04-06  

我费心写这个是由于list中可能会有重复记录
重复次数可能很多。。。。

1 楼 chenyulong1 2010-04-06  

不知博主是否己找到心怡的工作，看到这个帖子。写了两个方法。

public static List<String> union(List<String> one, List<String> two) {
		Set<String> t1 = new TreeSet<String>();
		t1.addAll(one);
		Set<String> t2 = new TreeSet<String>();
		t2.addAll(two);
		List<String> result = new ArrayList<String>();
		for (String s : t1.size() < t2.size() ? t1 : t2) {
			if (t1.size() < t2.size() ? t2.contains(s) : t1.contains(s)) {
				result.add(s);
			}
		}
		return result;
		
	}

	public static List<String> union(List<List<String>> list) {
		List<String> result = list.get(0);
		if (list.size() == 0)
			return result;
		for (int i = 1; i < list.size(); i++) {
			result = union(result, list.get(i));
		}
		return result;
	}