# Java Program to Find the Sum of n Square Numbers

This is the Java Program to Find the Sum of n Square Numbers.

Problem Description

Given an integer says n, find out the sum of the first n squared numbers.

Problem Solution

The sum of the first n squared numbers can be calculated using the formula :

sum = n*(n+1)*(2n+1)/6

Program/Source Code

Here is the source code of the Java Program to Find the Sum of n Square Numbers. The program is successfully compiled and tested using IDE IntelliJ Idea in Windows 7. The program output is also shown below.

1. ` `
2. `//Java Program to Find the Sum of n Square Numbers`
3. ` `
4. `import java.io.BufferedReader;`
5. `import java.io.InputStreamReader;`
6. ` `
7. `public class SumOfNSquareNumbers {`
8. `    // Function to read n and display the sum`
9. `    public static void main(String[] args) {`
10. `        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));`
11. `        int n;`
12. `        System.out.println("Enter the value of n");`
13. `        try{`
14. `            n = Integer.parseInt(br.readLine());`
15. `        }catch (Exception e){`
16. `            System.out.println("An error occurred");`
17. `            return;`
18. `        }`
19. `        if(n<0){`
20. `            System.out.println("n cannot take negative values");`
21. `            return;`
22. `        }`
23. `        double sum = n*(n+1)*(2*n+1)/6;`
24. `        System.out.println("The sum of first " + n + " squared numbers is " + sum);`
25. `    }`
26. `}`
Program Explanation

In the function main(), firstly an integer n is entered and then the sum is calculated as per the line,
double sum = n*(n+1)*(2*n+1)/6. Finally, the sum is displayed.

Time Complexity: O(1).

Runtime Test Cases
```
Case 1 (Simple Test Case):

Enter the value of n
15
The sum of first 15 squared numbers is 1240.0```

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