java foreach Iterator 性能差别

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package com.bp.test;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

/**
* 关于map的测试
* @author current_bp
* @createTime 20161111
*/
public class MapTest {

public static void main(String[] args) {

// MapTest.mapGetEachValue();
MapTest.mapGetEachValue2();
}

public static void mapGetEachValue(){
Map<String, String> map = new HashMap<>();

for(int i=0;i<100000;i++){
map.put("bp"+i, "baopan"+i);
}

Long time1 = System.currentTimeMillis();
for(String key : map.keySet()){
System.out.println("key:"+key+" value:"+map.get(key));
}
Long time2 = System.currentTimeMillis();
System.out.println("allTime:"+(time2 - time1));
//count:10000,valueCount:8,avg:144.875,allResult:[153,118,117,207,91,110,95,268]
//count:100000,valueCount:8,avg:989.5,allResult:[977,969,1002,1091,949,1116,956,856]

}

public static void mapGetEachValue2(){
Map<String, String> map = new HashMap<>();

for(int i=0;i<100000;i++){
map.put("bp"+i, "baopan"+i);
}

Long time1 = System.currentTimeMillis();
Iterator<String> iter = map.keySet().iterator();
String key = null;

while(iter.hasNext()){
key = iter.next();
System.out.println("key:"+key+" value:"+map.get(key));
}
Long time2 = System.currentTimeMillis();
System.out.println("allTime2:"+(time2 - time1));
//count:10000,valueCount:8,avg:138.375,allResult:[129,132,83,128,256,106,105,168]
//count:100000,valueCount:8,avg:965.875,allResult:[957,912,720,1116,958,977,1069,1018]

}
}

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