自己刚刚写的一个程式，感觉效率很低，求各位帮忙改一下。

import java.util.ArrayList;

import java.util.Collection;

import java.util.Collections;

import java.util.Comparator;

import java.util.Iterator;

import java.util.LinkedHashMap;

import java.util.List;

import java.util.Map;

import java.util.Map.Entry;

import java.util.Set;

import java.util.TreeMap;



/*

 * 将学生名和考试成绩录入到MAP中,并按照成绩显示前三名

 * 

 * */





public class Test2 {

	public static void main(String[] args)

	{

		TreeMap reporter =new TreeMap();

		

		reporter.put("D9", 99);

		reporter.put("D2", 92);

		reporter.put("D8", 19);

		reporter.put("D4", 39);

		reporter.put("D5", 59);

		reporter.put("D3", 79);

		reporter.put("D1", 69);

		

		Collection coll  = reporter.values();

		List l = new ArrayList(coll);

		Collections.sort(l,new Comparator(){



			@Override

			public int compare(Object o1, Object o2) {

				if(o1 instanceof Integer&&o2 instanceof Integer)

				{

					Integer i1 = (Integer)o1;

					Integer i2 = (Integer)o2;

					

					return i2.compareTo(i1);

				}

				return 0;

			}});

		

		LinkedHashMap lm = new LinkedHashMap();

		Set set = reporter.entrySet();

		for(int j=0;j<3;j++){

			Integer i  = (Integer) l.get(j);

			Iterator it = set.iterator();

			while(it.hasNext())

			{

				Map.Entry entry = (Entry) it.next();

				if((Integer)entry.getValue()==i){

				lm.put(entry.getKey(), entry.getValue());

			}

		}

		}

		System.out.println(lm);

		

		

	}



	

}