Java Program to Calculate Sum of n Natual Numbers

Last Updated: 17 August, 2022

On this tutorial page we are going to learn how to write a Java program to calculate the sum of N natural numbers.

Natural numbers are the positive integers from 1 to infinity, i.e., 1, 2, 3, 4, 5, 6, 7,... Natural numbers do not contain negative numbers or zero.

Natural numbers: 1,2,3,4,5, ....... n

In comparison to whole numbers, natural numbers include all the whole numbers excluding the number 0.

We can find sum of natural numbers in two ways, using mathematical formula or Java loops.

Sum of n natural numbers = n * (n + 1) / 2

Let's see the Java Programs given below.

Program 1: Find Sum of n Natural Numbers using Mathematical formula in Java

  public class SumOfNaturalNumbers {
    static int sumOfNaturalNumbers(int n) {
      // finding sum of n natural numbers using mathematical formula
      // Sum of n natural numbers = n*(n+1)/2
      return n * (n + 1) / 2;
    }
  
    public static void main(String args[]) {
      int n = 10;
      // calling the method and printing the sum of natural numbers 10.
      System.out.println("Sum of Natural Numbers " + n + " is: " + sumOfNaturalNumbers(n));
    }
  }

Output

Sum of Natural Numbers 10 is: 55

Program 2: Find Sum of n Natural Numbers using for loop in Java

  public class SumOfNaturalNumbers {
    public static void main(String[] args) {
      int num = 50, sumValue = 0;
      
      // Adding: 1 + 2 + 3 + 4... + 50
      for (int i = 1; i <= num; ++i) {
        sumValue = sumValue + i;
      }
  
      System.out.println("Sum of 1 to 50 natural numbers: " + sumValue);
    }
  }

Output

Sum of 1 to 50 natural numbers: 1275

Program 3: Find Sum of n Natural Numbers using while loop in Java with User Input

  
  import java.util.Scanner;
  public class SumOfNaturalNumbers2 {
    public static void main(String[] args) {
      Scanner scanner = new Scanner(System.in);
      System.out.print("Number beginning from: ");
      int firstNum = scanner.nextInt();
      
      System.out.print("Number ended: ");
      int lastNum = scanner.nextInt();
      
      scanner.close();
      
      int sumValue = 0;
      
      while (firstNum <= lastNum) {
        sumValue = sumValue + firstNum;
        firstNum++;
      }
      System.out.println("Sum: " + sumValue);
    }
  }

Output

Number beginning from: 5
Number ended: 15
Sum: 110