Several ways to get the key value of a map

1. Call the keySet method:

	@Test
    public void getKeys1(){
        Map<String, Object> map = new HashMap<>();
        map.put("name","Cao Cao");
        map.put("sex","male");
        map.put("age","21");
        System.out.println("():"+map.keySet());
        Iterator<String> iterator = map.keySet().iterator();
        while (iterator.hasNext()){
            System.out.println("iterator:"+iterator.next());
        }
        Set<String> keySet = map.keySet();
        // Iterate through the keySet and output the value of the key
        for(String key : keySet){
            System.out.println(key+":"+map.get(key).toString());
        }
    }

Output:

():[sex, name, age]
 iterator:sex
 iterator:name
 iterator:age
 sex: male
 name: Cao Cao
 age:21

2. entrySet()

    @Test
    public void getKeys2(){
        Map<String, Object> map = new HashMap<>();
        map.put("name","Cao Cao");
        map.put("sex","male");
        map.put("age","21");
        //The second type
        System.out.println("():"+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());
        }
    }

Output:

():[sex=male, name=Cao Cao, age=21]
 iterator:sex=Male
 iterator:name=Cao Cao
 iterator:age=21
 key:sex;value:male
 key:name;value: Cao Cao
 key:age;value:21

Reference link:
/cailijuan/p/