获取Map的key值的几种方式

1. 调用keySet方法：

   @Test
   public void getKeys1(){
       Map map = new HashMap<>();
       map.put("name","曹操");
       map.put("sex","男");
       map.put("age","21");
       System.out.println("map.keySet():"+map.keySet());
       Iterator iterator = map.keySet().iterator();
       while (iterator.hasNext()){
           System.out.println("iterator:"+iterator.next());
       }
       Set 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

2. entrySet()

   @Test
   public void getKeys2(){
       Map 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> iterator = map.entrySet().iterator();
       while (iterator.hasNext()){
           System.out.println("iterator:"+iterator.next());
       }
       for (Map.Entry 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