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Program: Basic HashSet Operations.


Below example shows basic operations on HashSet object like creating object, adding elements, verifying whether the hashset is empty or not, removing an element, size of the hashset, and to check whether an object exists or not.

package com.java2novice.hashset;

import java.util.HashSet;

public class MyBasicHashSet {

        public static void main(String a[]){
                HashSet<String> hs = new HashSet<String>();
                //add elements to HashSet
                System.out.println("Is HashSet empty? "+hs.isEmpty());
                System.out.println("Size of the HashSet: "+hs.size());
                System.out.println("Does HashSet contains first element? "+hs.contains("first"));

[second, third, first]
Is HashSet empty? false
[second, first]
Size of the HashSet: 2
Does HashSet contains first element? true
Next Program >>

List Of All HashSet Sample Programs:

  1. Basic HashSet Operations.
  2. How to iterate through HashSet?
  3. How to copy Set content to another HashSet?
  4. How to delete all elements from HashSet?
  5. How to copy all elements from HashSet to an array?
  6. How to compare two sets and retain elements which are same on both sets?
  7. How to eliminate duplicate user defined objects from HashSet?
  8. How to find user defined objects from HashSet?
  9. How to delete user defined objects from HashSet?
Knowledge Centre
What is wrapper class?
Everything in java is an object, except primitives. Primitives are int, short, long, boolean, etc. Since they are not objects, they cannot return as objects, and collection of objects. To support this, java provides wrapper classes to move primitives to objects. Some of the wrapper classes are Integer, Long, Boolean, etc.
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About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected].

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java™ Platform Standard Ed. 8 - API Specification | Java is registered trademark of Oracle.
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