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!!!!!!!!");
		
		
	}
}

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？