Check If TreeSet is Empty in Java Example

This example shows how to check if TreeSet is empty in Java. This example also shows how to check if the TreeSet object is empty using isEmpty and size methods.

How to check if TreeSet is empty in Java?

The TreeSet is called empty if there are no elements in the set object. There are a couple of ways to check that as given below.

1. Using the TreeSet isEmpty method

The isEmpty method of the TreeSet class returns true if the TreeSet object is empty.

1	public boolean isEmpty()

The isEmpty method returns a boolean value indicating whether there are any elements in the set object. It returns true if there are no elements present in the set object, false if there is at least one element present in the TreeSet object.

import java.util.TreeSet;

public class CheckIfTreeSetIsEmptyExample {

public static void main(String[] args) {

TreeSet<String> tSetCharacters = new TreeSet<String>();

* To check if the TreeSet is empty, use the

* isEmpty method.

* It returns true if there are no elements in the TreeSet.

//this will return true as the set is empty

System.out.println( tSetCharacters.isEmpty() );

//add some elements

tSetCharacters.add("z");

tSetCharacters.add("a");

//this will return false as there are two elements in the TreeSet object

System.out.println( tSetCharacters.isEmpty() );

}

Output

1 2	true false

2. Using the size method

We can also use the size method to check the same. The size method returns the number of elements stored in the TreeSet object.

1	public int size()

We can compare the return value of the size method with 0 to check if the set object is empty or not as given below.

import java.util.TreeSet;

public class CheckIfTreeSetIsEmptyExample {

public static void main(String[] args) {

TreeSet<String> tSetCharacters = new TreeSet<String>();

* Compare the return value of the size method with 0

* to check

//this will return true as the set is empty

System.out.println( tSetCharacters.size() == 0 );

//add an element

tSetCharacters.add("d");

tSetCharacters.add("c");

//this will return false as there are two elements in the TreeSet object

System.out.println( tSetCharacters.size() == 0 );

}

Output

1 2	true false

Please visit the how to check the TreeSet size example to know more.

Which method should I use to check?

The TreeSet class internally maintains an instance of a NavigableMap to store the elements. Both the size method and isEmpty method calls the size method and isEmpty method of this map instance respectively.

The size and isEmpty methods of the map use the same size reference, so the performance should be the same for both of these methods.

However, when it comes to the readability of the code, the isEmpty method is more readable and shows the clear intent of the code as compared to using the size method for this purpose. That is why using the isEmpty method is the preferred way to check if the TreeSet is empty or not.

This example is a part of the Java TreeSet Tutorial with Examples.

Please let me know your views in the comments section below.

References:
Java 8 TreeSet