Personal Understanding of HashSet

HashSet: The underlying implementation is hashmap.

[Java]
Public class HashSet <E>
Extends AbstractSet <E>
Implements Set <E>, Cloneable, java. io. Serializable
{
 
Private transient HashMap <E, Object> map;
// Actually, HashSet references HashMap. The value of set is the Key of HashMap.
// All operations are based on HashMap.
For example:
Public boolean add (E e ){
Return map. put (e, PRESENT) = null;
}
// The PRESENT is only used for filling and has no practical significance.
Private static final Object PRESENT = new Object ();
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