遍历数组 iterator方法和for方法

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

public class ArrayTest {
public static void main(String[] args) {
List list = new ArrayList();
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);    }}

}