遍历数组 iterator方法和for方法

下面的程序可以看出他们之间的区别与联系：

import java.util.ArrayList;import java.util.Iterator;import java.util.List;public class ArrayTest {    public static void main(String[] args) {        List<Integer> list = new ArrayList<Integer>();        list.add(1);        list.add(2);        list.add(3);        System.out.println("用for循环遍历");        for (int i = 0; i < list.size(); i++) {            System.out.println(list.get(i));        }        System.out.println("用增强for循环");        for (Integer i : list) {            System.out.println(i);        }        System.out.println("用iterator+while");        Iterator<Integer> it = list.iterator();        while (it.hasNext()) {            int i = (Integer) it.next();            System.out.println(i);        }        System.out.println("用iterator+for");        for (Iterator<Integer> iter = list.iterator(); iter.hasNext();) {            int i = (Integer) iter.next();            System.out.println(i);        }    }}