HashSet底层代码实现原理

提示：本文章参考jdk1.8

 HashSet set = new HashSet<>();

    private transient HashMap map;

    // Dummy value to associate with an Object in the backing Map
    private static final Object PRESENT = new Object();

 public HashSet() {
 //创建HashSet对象时，同时底层也创建了HashMap<>（）对象
        map = new HashMap<>();
    }
  

     //HashSet的add（）方法中储存数据相当于向HashMap的put（）方法中储存数据
  public boolean add(E e) {
  
        return map.put(e, PRESENT)==null;
    }