Map的四种遍历方式

 1 public static void main(String[] args) {
 2         Map<String, String> testMap = new HashMap();
 3         testMap.put("key1", "value1");
 4         testMap.put("key2", "value2");
 5         testMap.put("key3", "value3");
 6 
 7         //第一种：二次取值，使用较多的一种
 8         for (String key : testMap.keySet()) {
 9             System.out.println("key:" + key + ",value:" + testMap.get(key));
10         }
11         //第二种：利用interator遍历
12         Iterator iterator =  testMap.entrySet().iterator();
13         while (iterator.hasNext()) {
14             Map.Entry<String, String> entry = (Map.Entry<String, String>) iterator.next();
15             System.out.println("key:" + entry.getKey() + ",value:" + entry.getValue());
16         }
17         //第三种：通过entrySet遍历 推荐,尤其容量大
18         for (Map.Entry<String, String> entry : testMap.entrySet()) {
19             System.out.println("key:" + entry.getKey() + ",value:" + entry.getValue());
20         }
21         //第四种：只遍历value，不可遍历key
22         for (String value : testMap.values()) {
23             System.out.println("value:" + value);
24         }
25     }