Java – underlying datastructure of HashSet

For ArrayList, the basic datastructure is array. For LinkedList, it is a link object. For HashMap or hashtable, it can be an array of LinkedList or tree. What is the data structure used in HashSet

Solution

According to the Javadoc, the backup data structure of HashSet is HashMap

The JDK 1.6 code verifies this:

public HashSet() {
    map = new HashMap<>();
}