MAP遍历的几种方式

 1 public static void main(String[] args) {
 2 
 3 
 4   Map<String, String> map = new HashMap<String, String>();
 5   map.put("1", "value1");
 6   map.put("2", "value2");
 7   map.put("3", "value3");
 8   
 9   //第一种：普遍使用，二次取值
10   System.out.println("通过Map.keySet遍历key和value：");
11   for (String key : map.keySet()) {
12    System.out.println("key= "+ key + " and value= " + map.get(key));
13   }
14   
15   //第二种
16   System.out.println("通过Map.entrySet使用iterator遍历key和value：");
17   Iterator<Map.Entry<String, String>> it = map.entrySet().iterator();
18   while (it.hasNext()) {
19    Map.Entry<String, String> entry = it.next();
20    System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
21   }
22   
23   //第三种：推荐，尤其是容量大时
24   System.out.println("通过Map.entrySet遍历key和value");
25   for (Map.Entry<String, String> entry : map.entrySet()) {
26    System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
27   }
28 
29   //第四种
30   System.out.println("通过Map.values()遍历所有的value，但不能遍历key");
31   for (String v : map.values()) {
32    System.out.println("value= " + v);
33   }
34  }