获取Map的key值的几种方式

秒速五厘米 2023-06-30 05:29 10阅读 0赞

1.  调用keySet方法：

@Test
        public void getKeys1(){ 
            Map<String, Object> map = new HashMap<>();
            map.put("name","曹操");
            map.put("sex","男");
            map.put("age","21");
            System.out.println("map.keySet():"+map.keySet());
            Iterator<String> iterator = map.keySet().iterator();
            while (iterator.hasNext()){ 
                System.out.println("iterator:"+iterator.next());
            }
            Set<String> keySet = map.keySet();
            // 遍历keySet，并输出key的值
            for(String key : keySet){ 
                System.out.println(key+":"+map.get(key).toString());
            }
        }

输出：

map.keySet():[sex, name, age]
    iterator:sex
    iterator:name
    iterator:age
    sex:男
    name:曹操
    age:21

1.  entrySet()

@Test
        public void getKeys2(){ 
            Map<String, Object> map = new HashMap<>();
            map.put("name","曹操");
            map.put("sex","男");
            map.put("age","21");
            //第二种
            System.out.println("map.entrySet():"+map.entrySet());
            Iterator<Map.Entry<String, Object>> iterator = map.entrySet().iterator();
            while (iterator.hasNext()){ 
                System.out.println("iterator:"+iterator.next());
            }
            for (Map.Entry<String, Object> entry : map.entrySet()){ 
                System.out.println("key:"+entry.getKey()+";value:"+entry.getValue());
            }
        }

输出：

map.entrySet():[sex=男, name=曹操, age=21]
    iterator:sex=男
    iterator:name=曹操
    iterator:age=21
    key:sex;value:男
    key:name;value:曹操
    key:age;value:21

参考链接：  
[https://www.cnblogs.com/cailijuan/p/10687995.html][https_www.cnblogs.com_cailijuan_p_10687995.html]

[https_www.cnblogs.com_cailijuan_p_10687995.html]: https://www.cnblogs.com/cailijuan/p/10687995.html