Map四种遍历方式

      Map<String, String> map = new HashMap<String, String>();        map.put("key1", "value1");        map.put("key2", "value2");        map.put("key3", "value3");                //第一种：普遍使用，二次取值        System.out.println("通过Map.keySet遍历key和value：");        for (String key : map.keySet()) {         System.out.println("key= "+ key + " and value= " + map.get(key));        }                //第二种        System.out.println("通过Map.entrySet使用iterator遍历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());        }              <span style="color:#FF0000;">  //第三种：推荐，尤其是容量大时</span>        System.out.println("通过Map.entrySet遍历key和value");        for (Map.Entry<String, String> entry : map.entrySet()) {         System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());        }              //第四种        System.out.println("通过Map.values()遍历所有的value，但不能遍历key");        for (String v : map.values()) {         System.out.println("value= " + v);        }