Java program to calculate the sum of natural numbers

Java program to calculate the sum of natural numbers using loops

In this tutorial, we will discuss a concept of Java program to calculate the sum of natural numbers using loops

In this article, we are going to learn  how to  find the sum of natural numbers using loops in the Java programming language

Java code to find the sum of numbers using for loop

Program 1

This program takes input from the user and stores in variable num. Then, the for loop is used to calculate the sum of natural numbers up to the given number.

import java.util.Scanner;
class NaturalSum1{
public static void main(String args[]){
    int sum=0;          //variable declaration
    Scanner scan=new Scanner(System.in);
                        //create a scanner object for input

System.out.print("Enter the number to find sum: ");
int num=scan.nextInt();

for(int i=1; i<=num; i++){
sum+=i;  //sum=sum+i;

}
System.out.println("Sum of the numbers until "+num +":"+sum);  //display result
}
}

When the above code is executed, it produces the following results

Enter the number to find sum: 15
Sum of the natural numbers until 15 : 120

Java code to find the sum of numbers using while loop

Program 2

This program takes input from the user and stores in variable num. Then, the while loop is used to calculate the sum of natural numbers up to the given numbers.

import java.util.Scanner;
class NaturalSum2{
public static void main(String args[]){
    int sum=0;  //variable declaration
    Scanner scan=new Scanner(System.in);
//create a scanner object for input

System.out.print("Enter the number to find sum: ");
int num=scan.nextInt();
int i=1;
while( i<=num){
sum+=i;  //sum=sum+i;
 i++;
}
System.out.println("Sum of the numbers until "+num +":"+sum);
}
}

When the above code is executed, it produces the following results

Enter a number to find sum: 25
Sum of the numbers until 25: 325

Java code to find the sum of numbers using do-while loop

Program 3

This program takes input from the user and stores in variable num. Then, the do-while loop is used to calculate the sum of natural numbers up to the given number.

import java.util.Scanner;
class NaturalSum3{
public static void main(String args[]){
    int sum=0;  //variable declaration     //1
    Scanner scan=new Scanner(System.in);
//create a scanner object for input

System.out.print("Enter the number to calculate sum: ");
int num=scan.nextInt();   //2
int i=1;
do{          //3
sum+=i;  //sum=sum+i;
 i++;
}
while( i<=num);
System.out.println("Sum of the numbers until "+num +":"+sum);  //4
}
}

When the above code is executed, it produces the following results

Enter a number to calculate sum: 50
Sum of the numbers until 50: 1275

Method:

1. The following variables i,num and sum=0 are declared.
2. A positive integer is received from the user.
3. Then, the loop is used to add a consecutive number from 1 up to the given number.
4. Finally, the sum is received as output and displayed.

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