Map 遍历的几种方法

复习map的过程中想到的，做个简单的记录

public class HashMapTest {

    public static void main(String args[]) {
        Map<Integer, Integer> hm = new HashMap<Integer, Integer>();
        hm.put(1, 8);
        hm.put(2, 7);
        hm.put(3, 6);
        hm.put(4, 5);
        System.out.println(hm);
        System.out.println("第一种：foreach循环");
        for (Integer i : hm.keySet()) {
            Integer a = hm.get(i);
            System.out.println(a);
        }

        System.out.println("第二种：迭代器");
        Iterator<Map.Entry<Integer, Integer>> it = hm.entrySet().iterator();
        while (it.hasNext()) {
            System.out.println(it.next().getValue());
        }

        System.out.println("第三种：");
        for (Map.Entry<Integer, Integer> entry : hm.entrySet()) {
            System.out.println(entry.getKey() + "--" + entry.getValue());
        }

    }

}