java的遍历数组效率测试源码[通俗易懂]

package javatest;

import java.util.ArrayList;

import java.util.Iterator;
import java.util.List;

public class javatest {

	public static void main(String[] args) {
		List<String> list = new ArrayList<String>();
		long t1,t2;
		for(int j = 0; j < 10000000; j++){
			list.add("aaaaaabbbbbbbcccccccc");
		}
		//==================== 方式 1 =========================
		t1=System.currentTimeMillis();
		for(String tmp:list){
			//System.out.println(tmp);
		}
		t2=System.currentTimeMillis();
		System.out.println("List first visit method Run Time:" + (t2 -t1) + "(ms)");
		//==================== 方式 2 =========================
		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("List second visit method Run Time:" + (t2 -t1) + "(ms)");
		//===================== 方式 3 ========================
		Iterator<String> iter = list.iterator();
		t1=System.currentTimeMillis();
		while(iter.hasNext()){
			iter.next();
			//System.out.println(iter.next());
		}
		t2=System.currentTimeMillis();
		System.out.println("List Third visit method Run Time:" + (t2 -t1) + "(ms)");	
	}
}