In this post, You will learn today today how to find sum of first n numbers in java using while loop, for loop and mathematics formula(Optimized).
For this program, we have to input the natural number n value which you want to get the sum. So that Our program will get sum of first n numbers. This is basic program for freshers or who are studying engineering in their lab programs.
Example 1:
number = 10
sum = 55
Example 2:
number = 100
sum = 5050
Following are the example programs to find sum of first n or 10 or 100.
Finding first n numbers sum using while loop.
Output:
While loop examples programs.
In high school, you may have learnt formula or theorem to get sum of first n numbers. Now we will write a optimized program using the formula.
Formula : n*(n+1)/2
Compared to first and second options, this is requires less to calculate the sum.
First two takes O(n) time complexity but using formula it is in O(1).
Output:
For this program, we have to input the natural number n value which you want to get the sum. So that Our program will get sum of first n numbers. This is basic program for freshers or who are studying engineering in their lab programs.
Example 1:
number = 10
sum = 55
Example 2:
number = 100
sum = 5050
Following are the example programs to find sum of first n or 10 or 100.
1. Using For Loop:
Finding n numbers sum using for loop.
package blog.java.w3schools.sum.numbers;
import java.util.Scanner;
public class SumNForLoop {
public static void main(String[] args) {
System.out.println("Enter a number : ");
Scanner scanner = new Scanner(System.in);
int number = scanner.nextInt();
int sum = 0;
for (int i = 0; i <= number; i++) {
sum = sum + i;
}
System.out.println("Final sum of first " + number + " numbers using For loop is " + sum);
}
}
Output:
The above program takes input of n values and loop using for loop from 0 to n.
For loop examples programs.
Enter a number : 10
Final sum of first 10 numbers using For loop is 55
The above program takes input of n values and loop using for loop from 0 to n.
For loop examples programs.
2. Using While loop.
Finding first n numbers sum using while loop.
public class SumNWhileLoop {
public static void main(String[] args) {
System.out.println("Enter a number : ");
Scanner scanner = new Scanner(System.in);
int number = scanner.nextInt();
int sum = 0;
int i = 0;
while (i <= number) {
sum = sum + i;
i++;
}
System.out.println("Final sum of first " + number + " numbers using While loop is " + sum);
}
}
Output:
Enter a number : 10
Final sum of first 10 numbers using While loop is 55
While loop examples programs.
3. Using Arithmetic formula:
In high school, you may have learnt formula or theorem to get sum of first n numbers. Now we will write a optimized program using the formula.
Formula : n*(n+1)/2
Compared to first and second options, this is requires less to calculate the sum.
First two takes O(n) time complexity but using formula it is in O(1).
public class SumNFormula { public static void main(String[] args) { System.out.println("Enter a number : "); Scanner scanner = new Scanner(System.in); int number = scanner.nextInt(); int sum = 0; sum = number * (number + 1) / 2; System.out.println("Final sum of first " + number + " numbers using formula is " + sum); } }
Output:
Enter a number : 100
Final sum of first 100 numbers using formula is 5050
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