JavaSE-集合的遍历

package com.btp.t4;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Date;
import java.util.Iterator;

import org.junit.Test;

public class TestIterator {
	
	//正确的写法：使用迭代器实集合的遍历
	@Test
	public void Test1(){
		Collection coll=new ArrayList();
		coll=Arrays.asList(123,"AA",new Date(),"BB");
		
		System.out.println(coll);
		
		Iterator i=coll.iterator();
		while(i.hasNext()){
			System.out.println(i.next());
		}
	}
	
	//正确的写法：使用增强foreach循环实现集合的遍历
	@Test
	public void Test3(){
		Collection coll=new ArrayList();
		coll=Arrays.asList(123,"AA",new Date(),"BB");
		
		System.out.println(coll);
		for(Object obj:coll)//obj是一个新定义的局部变量，修改obj不会修改coll的值
		{
			System.out.println(obj);
		}
	}
	
	//错误的写法
	@Test
	public void Test2(){
		Collection coll=new ArrayList();
		coll=Arrays.asList(123,"AA",new Date(),"BB");
		System.out.println(coll);
		
		Iterator i=coll.iterator();
		while(i.next()!=null){
			System.out.println(i.next());
		}
	}
}