java list三种遍历方法性能比较

    从c/c++语言转向java开发，学习java语言list遍历的三种方法，顺便测试各种遍历方法的性能，测试方法为在ArrayList中插入1千万条记录，然后遍历ArrayList，发现了一个奇怪的现象，测试代码如下：

 

package com.hisense.tiger.list;



import java.util.ArrayList;

import java.util.Iterator;

import java.util.List;



public class ListTest {

	public static void main(String[] args)

	{

		List<String> list = new ArrayList<String>();

		long t1,t2;

		for(int j = 0; j < 10000000; j++)

		{

			list.add("aaaaaa" + j);

		}

		System.out.println("List first visit method:");

		t1=System.currentTimeMillis();

		for(String tmp:list)

		{

			//System.out.println(tmp);

		}

		t2=System.currentTimeMillis();

		System.out.println("Run Time:" + (t2 -t1) + "(ms)");

		System.out.println("List second visit method:");

		

		t1=System.currentTimeMillis();

		for(int i = 0; i < list.size(); i++)

		{

			list.get(i);

			//System.out.println(list.get(i));

		}

		t2=System.currentTimeMillis();

		System.out.println("Run Time:" + (t2 -t1) + "(ms)");

		

		System.out.println("List Third visit method:");

		Iterator<String> iter = list.iterator();

		

		t1=System.currentTimeMillis();

		while(iter.hasNext())

		{

			iter.next();

			//System.out.println(iter.next());

		}

		t2=System.currentTimeMillis();

		System.out.println("Run Time:" + (t2 -t1) + "(ms)");

				

		System.out.println("Finished!!!!!!!!");

		

		

	}

}

 

    测试结果如下：

List first visit method:
Run Time:170(ms)
List second visit method:
Run Time:10(ms)
List Third visit method:
Run Time:34(ms)
Finished!!!!!!!!

    测试的结论很奇怪，第一种方法是java语言支持的新语法，代码最简洁，但是在三种方法中，性能确是最差的，取size进行遍历性能是最高的，求牛人解释？