Map的四種遍歷方式

      Map<String, String> map = new HashMap<String, String>();
      map.put("1", "value1");
      map.put("2", "value2");
      map.put("3", "value3");
      
      //第一種：普遍使用，二次取值
      System.out.println("通過Map.keySet遍歷key和value：");
      for (String key : map.keySet()) {
       System.out.println("key= "+ key + " and value= " + map.get(key));
      }
      
      //第二種
      System.out.println("通過Map.entrySet使用iterator遍歷key和value：");
      Iterator<Map.Entry<String, String>> it = map.entrySet().iterator();
      while (it.hasNext()) {
       Map.Entry<String, String> entry = it.next();
       System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
      }
      
      //第三種：推薦，尤其是容量大時
      System.out.println("通過Map.entrySet遍歷key和value");
      for (Map.Entry<String, String> entry : map.entrySet()) {
       System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
      }
    
      //第四種
      System.out.println("通過Map.values()遍歷所有的value，但不能遍歷key");
      for (String v : map.values()) {
       System.out.println("value= " + v);
      }
     }

內容來源：www.runoob.com