Skip to content
Related Articles

Related Articles

Improve Article
TreeSet first() Method in Java
  • Last Updated : 26 Nov, 2018

The Java.util.TreeSet.first() method is used to return the first of the element of a TreeSet. The first element here is being referred to the lowest of the elements in the set. If the elements are of integer types then the smallest integer is returned. If the elements are of the string types then the elements are checked in the alphabetical order and the string starting with the initial alphabets in the order of dictionary is returned irrespective of length.

Syntax:

Tree_Set.first()

Parameters: The method does not take any parameters.

Return Value: The method returns the lowest member of the set. If the elements are of string type then they are checked in alphabetical order irrespective of length and if the elements are of integer types then the smallest integer is returned. Also, the numbers of string type hold higher priority.

Below are the programs illustrating the use of Java.util.TreeSet.first() method:
Program 1: When the elements are of integer types.






// Java code to illustrate first()
import java.util.*;
import java.util.TreeSet;
  
public class TreeSetDemo {
    public static void main(String args[])
    {
        // Creating an empty TreeSet
        TreeSet<Integer> tree = new TreeSet<Integer>();
  
        // Use add() method to add elements into the Set
        tree.add(14);
        tree.add(8);
        tree.add(200);
        tree.add(48);
        tree.add(7);
        tree.add(124);
  
        // Displaying the TreeSet
        System.out.println("TreeSet: " + tree);
  
        // Displaying the lowest element of the set
        System.out.println("The first element is: " + tree.first());
    }
}
Output:
TreeSet: [7, 8, 14, 48, 124, 200]
The first element is: 7

Program 2: When the elements are of string types.




// Java code to illustrate first()
import java.util.*;
import java.util.TreeSet;
  
public class TreeSetDemo {
    public static void main(String args[])
    {
        // Creating an empty TreeSet
        TreeSet<String> tree = new TreeSet<String>();
  
        // Use add() method to add elements into the Set
        tree.add("Welcome");
        tree.add("To");
        tree.add("Geeks");
        tree.add("Ab");
        tree.add("TreeSet");
        tree.add("B");
  
        // Displaying the TreeSet
        System.out.println("TreeSet: " + tree);
  
        // Displaying the lowest element of the set
        System.out.println("The first element is: " + tree.first());
    }
}
Output:
TreeSet: [Ab, B, Geeks, To, TreeSet, Welcome]
The first element is: Ab

Program 3: When the elements are of string types but with integer values. Here we see that the digit appearing first is considered as first element irrespective of length:




// Java code to illustrate first()
import java.util.*;
import java.util.TreeSet;
  
public class TreeSetDemo {
    public static void main(String args[])
    {
        // Creating an empty TreeSet
        TreeSet<String> tree = new TreeSet<String>();
  
        // Use add() method to add elements into the Set
        tree.add("Welcome");
        tree.add("To");
        tree.add("Geeks");
        tree.add("45");
        tree.add("100");
        tree.add("5");
  
        // Displaying the TreeSet
        System.out.println("TreeSet: " + tree);
  
        // Displaying the lowest element of the set
        System.out.println("The first element is: " + tree.first());
    }
}
Output:
TreeSet: [100, 45, 5, Geeks, To, Welcome]
The first element is: 100

Attention reader! Don’t stop learning now. Get hold of all the important Java Foundation and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready. To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.




My Personal Notes arrow_drop_up
Recommended Articles
Page :