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

 1 public class HashMapTest {
 2
 3     public static void main(String args[]) {
 4         Map<Integer, Integer> hm = new HashMap<Integer, Integer>();
 5         hm.put(1, 8);
 6         hm.put(2, 7);
 7         hm.put(3, 6);
 8         hm.put(4, 5);
 9         System.out.println(hm);
10         System.out.println("第一种：foreach循环");
11         for (Integer i : hm.keySet()) {
12             Integer a = hm.get(i);
13             System.out.println(a);
14         }
15
16         System.out.println("第二种：迭代器");
17         Iterator<Map.Entry<Integer, Integer>> it = hm.entrySet().iterator();
18         while (it.hasNext()) {
19             System.out.println(it.next().getValue());
20         }
21
22         System.out.println("第三种：");
23         for (Map.Entry<Integer, Integer> entry : hm.entrySet()) {
24             System.out.println(entry.getKey() + "--" + entry.getValue());
25         }
26
27     }
28
29 }