Find Sum of Series 1 + 2 + 3 + 4 + ... + n in Java

In this program, we'll compute the sum of the series 1/1! + 2/2! + 3/3! + ... + n/n! using Java. This involves calculating factorials and summing the results of each term divided by its factorial. We'll use Java's basic arithmetic, loop control, and built-in classes to achieve this.

Problem Statement

Write a Java program to calculate the sum of the series 1/1! + 2/2! + 3/3! + ... + n/n! and print the result.

Steps to find the sum of a series

Following are the steps to find the sum of a series ?

• Import necessary classes from java.io and java.lang package.
• Initialize variables for the sum and factorial calculation.
• To iterate we will implement a for loop.
• We will update factorial_val to calculate the factorial of the current integer and then add the result of i / i! to the sum.
• After the loop, return the computed sum.
• Print the result.
  

Java program to find the sum of a series

Below is the Java program to find the sum of a series 1/1! + 2/2! + 3/3! + 4/4! +??.+ n/n ?

import java.io.*;
import java.lang.*;
public class Demo{
   public static double pattern_sum(double val){
      double residual = 0, factorial_val = 1;
      for (int i = 1; i <= val; i++){
         factorial_val = factorial_val * i;
         residual = residual + (i / factorial_val);
      }
      return (residual);
   }
   public static void main(String[] args){
      double val = 6;
      System.out.println("The sum of the series is : " + pattern_sum(val));
   }
}

Output

The sum of the series is : 2.7166666666666663

Code Explanation

A class named Demo contains a function named ?pattern_sum'. This function takes a double-valued number as a parameter, and iterates through the value and calculates the series value of (1/1! + 2/2! + ..) and so on. In the main function, the value is defined and the function ?pattern_sum' is called by passing this value. The output is displayed on the console.