测试keySet()与entrySet()

import java.util.Calendar;   
import java.util.Date;   
import java.util.HashMap;   
import java.util.Iterator;   
import java.util.Map.Entry;   
  
/**  
 * 测试keySet()与entrySet()的迭代时间  
 * keySet():迭代后只能通过get()取key  
 * entrySet():迭代后可以e.getKey(),e.getValue()取key和value。返回的是Entry接口  
 * 最后说明下keySet()的速度比entrySet()慢了很多。看来以后要考虑用entrySet()了  
 * @author YL  
 * @date 2009.6.10  
 */  
public class HashMapTest       
{   
    public static void main(String[] args)    
    {   
        HashMap<String,String> kmap = new HashMap<String,String>();   
        HashMap<String, String> emap = new HashMap<String, String>();   
           
        //装数据   
        for (int i = 0; i < 1000; i++)    
        {   
            kmap.put(""+i, "YL");   
        }   
        for (int i = 0; i < 1000; i++)    
        {   
            emap.put(""+i, "ZT");   
        }   
           
        long stimes = System.currentTimeMillis();   
        long ctimes = Calendar.getInstance().getTimeInMillis();   
        long dtimes = new Date().getTime();   
           
        //初始时间 这里我用了三种取值方式 最后发现System.currentTimeMillis();是最直接的取值方法   
        System.out.println(stimes+" "+ctimes+"  "+dtimes);   
           
        Iterator<String> ktor = kmap.keySet().iterator();   
        while(ktor.hasNext())   
        {   
            System.out.println(ktor.next());   
        }   
           
        long stimes1 = System.currentTimeMillis();   
        long ctimes1 = Calendar.getInstance().getTimeInMillis();   
        long dtimes1 = new Date().getTime();   
           
        //结束世界并且也是entrySet的开始时间   
        System.out.println((stimes1-stimes)+"   "+(ctimes1-ctimes)+"    "+(dtimes1-dtimes));   
        System.out.println(stimes1+"    "+ctimes1+" "+dtimes1);   
           
        Iterator<Entry<String, String>> itor = emap.entrySet().iterator();   
        while(itor.hasNext())   
        {   
            Entry<String, String> e = itor.next();   
            //System.out.println(e.getKey());   
            System.out.println(e.getValue());   
        }   
           
        long stimes2 = System.currentTimeMillis();   
        long ctimes2 = Calendar.getInstance().getTimeInMillis();   
        long dtimes2 = new Date().getTime();   
        System.out.println(stimes2+"    "+ctimes2+" "+dtimes2);   
        System.out.println((stimes2-stimes1)+"  "+(ctimes2-ctimes1)+"   "+(dtimes2-dtimes1));   
    }   
}  

 

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