从bbs中看到的问题：从大量数据中取top100，整理的思路

TreeSet算法很强悍，以后一定要记得使用

package com;

import java.util.Iterator;
import java.util.Random;
import java.util.TreeSet;

import com.wfy.util.TimeUtil;

import sun.reflect.generics.tree.Tree;

public class TestMain {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Random rd = new Random();
		
		int rb = 1024*1024;
		int a = 100000000;
		int[] test = new int[a];
		for (int i = 0; i < a; i++) {
			test[i] = rd.nextInt();
		}
		TreeSet<Integer> tree = new TreeSet<Integer>();
		
		System.out.println("开始："+TimeUtil.dateTime1());
		for (int i = 0; i < a; i++) {
			if(tree.size()<100){
				tree.add(test[i]);
			}else{
				if( tree.first() < test[i] ){
					tree.remove( tree.first() );
					tree.add( test[i] );
				}
			}
		}
		System.out.println("结束："+TimeUtil.dateTime1());
		Iterator<Integer> iterator = tree.iterator();
		while(iterator.hasNext()){
			System.out.println(iterator.next());
		}
	}

}

 

评论

1 楼 lbxhappy 2012-07-06  

那如果tree.first()一开始就是最大的呢？是不是以后
else{ 
                if( tree.first() < test[i] ){ 
                    tree.remove( tree.first() ); 
                    tree.add( test[i] ); 
                } 
这段代码就不执行了