java list三种遍历方法性能比较

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中插入记录，然后遍历ArrayList，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!!!!!!!!");

	}

}

第一种:

   for(Iterator<A>    it    =    list.iterator();    it.hasNext();    )    {   

　　　　it.next();

       ....

   }

第二种:

   for(A    a    :    list)    {

       .....

   }

第三种:

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

       A    a    =    list.get(i);

       ...

   }

``