On this document we will be showing a java example on how to use the size() method of HashSet Class. Basically this method returns how many elements does our HashSet contains. Make a note that a HashSet is unsorted thus the order of elements are random, better watch out on this concept.

The HashSet as majority of the Collection classes make use of Generics such that if we have declared our set like HashSet set = new HashSet()  then the elements of inside our set is of type String. And we cannot insert different object type not unless its a subclass of the object declaration, otherwise a runtime error will be thrown.

The HashSet elements are unique, there would be no two identical elements that can exist.

Important notes for size() method:

  • specified by size in interface Collection
  • size in interface Set
  • size in class AbstractCollection

Method Syntax

public int size()

Method Argument

Data Type Parameter Description

Method Returns

The size() method returns the number of elements in this set (its cardinality).


Requires Java 1.2 and up

Java HashSet size() Example

Below is a java code demonstrates the use of size() method of HashSet class. The example presented might be simple however it shows the behavior of the szie() method.


import static java.lang.System.*;

import java.util.HashSet;

 * This example source code demonstrates the use of  
 * size() method of HashSet class

public class HashSetSizeExample {

	public static void main(String[] args) throws InterruptedException {

		// get the HashMap object from the method init()
		HashSet studentSet = init();
		// get and print the size of the set
		int size = studentSet.size();
		out.println("Size of student database is "+size);


	private static HashSet init() {
		// declare the HashSet object
		HashSet studentSet = new HashSet<>();
		// put contents to our HashMap
		studentSet.add("Shyra Travis");
		studentSet.add("Sharon Wallace");
		studentSet.add("Leo Batista");
		studentSet.add("Shyra Travis");
		return studentSet;


There are two methods created on the above example, main() and init. The main method calls the init() which initializes and assign values to a HashSet object. The main() method assign to a new HashSet object the returned object by the init() method. We then print the size of the set.

Sample Output

Below is the sample output when you run the above example.

HashSet size() example output