Java TreeSet - add() Method

The java.util.TreeSet.add() method is used to add a new element in the set. The element is added if it is not already present in the set.

Syntax

public boolean add(E element)

Here, E is the type of element maintained by the container.

Parameters

Return Value

Returns true if the element is successfully added, else returns false.

Exception

• Throws ClassCastException, if the specified object cannot be compared with the elements currently in this set.
• Throws NullPointerException, if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements.

Example:

In the example below, the java.util.TreeSet.add() method is used to add new element in the given set.

import java.util.*;

public class MyClass {
  public static void main(String[] args) {
    //creating a treeset
    TreeSet<Integer> MySet = new TreeSet<Integer>();

    //populating the set
    MySet.add(10);
    MySet.add(20);
    MySet.add(30);
    MySet.add(40);

    //printing the set
    System.out.println("MySet contains: " + MySet);   
  }
}

The output of the above code will be:

MySet contains: [10, 20, 30, 40]