HashSet

• HashSet in Java implements the Set interface of Collections Framework.
• It is used to store the unique elements and it doesn’t maintain any specific order of elements.
• HashSet can store the Null values.

Methods in Java HashSet

• add(E e)
  Used to add the specified element if it is not present, if it is present then return false.
• clear()
  Used to remove all the elements from the set.
• contains(Object o)
  Used to return true if an element is present in a set.
• remove(Object o)
  Used to remove the element if it is present in set.
• iterator()
  Used to return an iterator over the element in the set.
• isEmpty()
  Used to check whether the set is empty or not. Returns true for empty and false for a non-empty condition for set.
• size()
  Used to return the size of the set.
• clone()
  Used to create a shallow copy of the set.

import java.util.HashSet;
import java.util.Iterator;

class HashSetInJava{
    public static void main(String[] args){
        //Declaring the hashset
        HashSet <String> fruits= new HashSet<>();

        //Addding the elements to hashset
        fruits.add("Apple");
        fruits.add("Banana");
        fruits.add("Grapes");
        fruits.add("Mango");

        System.out.println("After adding elements: "+fruits);

        //remove Grapes from hashset
        fruits.remove("Grapes");

        System.out.println("After removing Grapes: "+fruits);

        //if element doesn't exist in hashset, it will return false
        fruits.remove("Grapes");
        System.out.println("Repeately remove Grapes: "+fruits.remove("Grapes"));

        //Iterating through the HashSet
        Iterator <String> iterate=fruits.iterator();
        System.out.print("Iterate through HashSet: ");
        while(iterate.hasNext()){
            System.out.print(iterate.next()+", ");
        }

    }
}