Java Program to Print the Sum of Series 1! + 2! + 3! + 4! + ….. + N!

In the previous article, we have discussed about Java Program to Display the Sum of Series (1+2)/(1*2) + (1+2+3)/(1*2*3) + …… + (1+2+3+…+N)/(1*2*3*…*N)

In this article we are going to see how to print the sum of series 1! + 2! + 3! + 4! + ….. + N! by using Java programming language

Java Program to Print the Sum of Series 1! + 2! + 3! + 4! + ….. + N!

In this series the it can be seen that numbers at each position i , the term is calculated as the factorial of i.

For example:

If at 3rd position the term is 3! = 6 and the sum up to 3rd position will be 1! + 2! + 3! = 1 + 2 + 6 = 9. 
Here, we for each we have to find the factorial of the number and add it to the sum.

Let’s see how to print the series.

By Using User Input Value
By Using User Defined Method
By Using Recursion

Method-1: Java Program to Print the Sum of Series 1! + 2! + 3! + 4! + ….. + N! By Using User Input Value

Approach:

Create Scanner class object.
Prompt the user to enter a number.
Initialize a variable sum to 0 of long data type(for larger values, int data type may overflow).
Run a for loop i=1 to n.
Inside the loop, initialize variable long fact = 1
Use another nested loop j=1 to i to find the factorial.
Inside the nested loop, update fact as fact *= j.
Outside the inner loop and inside the outer loop, update sum as sum = sum + fact.

Program:

import java.util.Scanner;
public class Main
{
    public static void main(String[] args)
    {
        // create a Scanner object
        Scanner sc = new Scanner(System.in);
        // prompt the user to enter the number of terms
        System.out.print("Enter the number of terms: ");
        int n = sc.nextInt();
        // call the method to print the series
        long sum = 0;
        for (int i = 1; i <= n; i++)
        {
            long fact = 1;
            for (int j = 1; j <= i; j++) 
            {
                fact *= j;
            }
            sum += fact;
        }
        System.out.print("The sum of the series is: " + sum);
    }

}

Output:

Enter the number of terms: 3
The sum of the series is: 9

Method-2: Java Program to Print the Sum of Series 1! + 2! + 3! + 4! + ….. + N! By Using User Defined Method

Approach:

Use the same approach as method 1 but move the nested loop inside a user-defined method

Program:

import java.util.Scanner;
public class Main
{
    public static void main(String[] args)
    {
        // create a Scanner object
        Scanner sc = new Scanner(System.in);
        // prompt the user to enter the number of terms
        System.out.print("Enter the number of terms: ");
        int n = sc.nextInt();
        // call the method to print the series
        long sum = 0;
        for (int i = 1; i <= n; i++) 
        {
            sum += fact(i);
        }
        System.out.print("The sum of the series is: " + sum);
    }
    private static long fact(int i) 
    {
        long fact = 1;
        for (int j = 1; j <= i; j++)
        {
            fact *= j;
        }
        return fact;
    }

}

Output:

Enter the number of terms: 5
The sum of the series is: 153

Method-3: Java Program to Print the Sum of Series 1! + 2! + 3! + 4! + ….. + N! By Calculating Factorial Value Using Recursion

Approach:

Use the same approach as method 2 but the user-defined method will calculate the factorial value recursively.

Define a method called fact which returns a double value take ‘n’ as an argument of int data type.
Inside the recursive method, check if (n == 1), return 1 (base condition).
Else return n*fact(n-1)

Program:

import java.util.Scanner;
public class Main 
{
    public static void main(String[] args) 
    {
        // create a Scanner object
        Scanner sc = new Scanner(System.in);
        // prompt the user to enter the number of terms
        System.out.print("Enter the number of terms: ");
        int n = sc.nextInt();
        // call the method to print the series
        long sum = 0;
        for (int i = 1; i <= n; i++)
        {
            sum += fact(i);
        }
        System.out.print("The sum of the series is: " + sum);
    }

    // method to calculate factorial recursively
    private static long fact(int n) 
    {
       // base condition
        if (n == 1)
            return 1;
        return n * fact(n-1);
    }

}

Output:

Enter the number of terms: 7
The sum of the series is: 5913

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