hash set in java geeks for geeeks
// predefined HashSet class
public class HashSet
{
// A HashMap object
private transient HashMap map;
// A Dummy value(PRESENT) to associate with an Object in the Map
private static final Object PRESENT = new Object();
// default constructor of HashSet class
// It creates a HashMap by calling
// default constructor of HashMap class
public HashSet() {
map = new HashMap<>();
}
// add method
// it calls put() method on map object
// and then compares it's return value with null
public boolean add(E e) {
return map.put(e, PRESENT)==null;
}
// Other methods in Hash Set
}