java list三种遍历方法性能比較

从c/c++语言转向java开发，学习java语言list遍历的三种方法，顺便測试各种遍历方法的性能，測试方法为在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，測试代码例如以下：

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!!!!!!!!");

}
}

測试结果例如以下：
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!!!!!!!!

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