Java program to calculate exponential e^x by using factorial and exp methods

Java program to calculate exponential of a given formula | Problem Solving in Java | AskTheCode

Problem:

The exponential e^x can be calculated using the formula:

e^x = 1 + x/1! + x^2/2! + x^3/3!+ ... x^n/n!

The factorial of non-negative integer n is written n! And is defined as follows:

n! = n * (n-1) * (n-2) * ... * 1

n! = 1 (if n = 0)


Write a Java program that contains two methods factorial and exp according to the formulas that we mentioned above. The main task for this program is to ask the user to enter a number and calculate its exponential, then display the result.


Sample input:

Enter a number: 8

Sample output:

The result is: 1765

Code:

import java.lang.*;
import java.io.*;

class Calc_Exponential{
	public static void main (String[] args) throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		System.out.print("Enter a number: ");
		int n = Integer.parseInt(br.readLine());
		int result = exp(n);
		System.out.print("The result is: "+result);
	}

	/* Method that returns factorial of a Number*/
	static int factorial(int n){
		if (n == 1) {
			return 1;
		}
		return n * factorial(n-1);
	}

	/* Method that calculates the exponential */
	static int exp(int n){
		int sum = 1;
		for (int i = 1; i <= n; i++) {
			sum += Math.pow(n, i) / factorial(i);
		}
		return sum;
	}
}
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