What is the TreeSet.first() function in Java?

The TreeSet.first() method obtains the first element in the TreeSet.

This method is present in the TreeSet class inside the java.util package.

Parameters

The TreeSet.first() method does not take any parameters.

Return

  • Element: It returns the lowest member of the TreeSet.

Example

Let’s understand with the help of an example.

We have a TreeSet: [1,8,5,3,9]

The first element in the TreeSet is 1.

The result of the TreeSet.first() method is 1.

Note: When we add the elements in the TreeSet, they get stored in the sorted form. If the TreeSet is of String type, the elements get stored in alphabetical order, irrespective of string length.

Code

Let’s take a look at the code snippet below.

import java.io.*;
import java.util.TreeSet;
class Main 
{
    public static void main(String args[])
    {
       TreeSet<Integer> tree_set = new TreeSet<Integer>();
       tree_set.add(1);
       tree_set.add(8);
       tree_set.add(5);
       tree_set.add(3);
       tree_set.add(0);
       System.out.println("First element of TreeSet is  " + tree_set.first());
    }
}

Explanation

  • In lines 1 and 2, we import the required packages and classes.

  • In line 4, we create a Main class.

  • In line 6, we create a main function.

  • In line 8, we declare a TreeSet of Integer type.

  • In lines 9 to 13, we add the elements into the TreeSet by using the TreeSet.add() method.

  • In line 14, we get the lowest member or the first element of the TreeSet using TreeSet.first() method and display the result with a message.

In this way, we can use the TreeSet.first() method to get the first element of the TreeSet.

Free Resources

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)