Simple Java HashSet example

This simple Java Example shows how to use Java HashSet. It also describes how to add something to HashSet object using add method.

import java.util.HashSet;

public class SimpleHashSetExample {

 public static void main(String[] args) {

  // create object of HashSet

  HashSet hSet = new HashSet();

  /**
   * Add an Object to HashSet using boolean add(Object obj) method of Java
   * HashSet class. This method adds an element to HashSet if it is not
   * already present in HashSet. It returns true if the element was added
   * to HashSet, false otherwise.
   **/

  System.out.println("Adding 1:" + hSet.add(1));
  System.out.println("Adding 2:" + hSet.add(2));
  System.out.println("Adding 3:" + hSet.add(3));

  /**
   * Adding element 2 second time returns false, because set can't occupy
   * duplicate elements.
   **/

  System.out.println("Adding 2:" + hSet.add(2));

  System.out.println("HashSet contains.." + hSet);
 }
}

The output is:



Adding 1:true
Adding 2:true
Adding 3:true
Adding 2:false
HashSet contains..[1, 2, 3]