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());
         }

     }

 }