Chapter 18, Problem 18.1PE

Program Plan Intro

Factorial

Program plan:

• Import required packages
• Declare the main class named “Main”.
  • Give the main method “public static void main ()”
    • Create an object “sc” for the scanner class.
    • Get a number from the user and store it in a variable “numberString”.
    • Create an object “bigNum” for the static method “BigInteger”.
    • Print the output.
  • Give function definition for the static method “factorial ()”.
    • Check if the value is equal to zero.
      • Return 1.
    • Else,
      • Call the function “factorial ()” recursively until the result is found.

Program Description Answer

The below program is used to find the factorial for the given number using “BigInteger” class.

Explanation of Solution

Program:

//Import required packages

import java.math.*;

import java.util.*;

//Class name

public class Main

{

//Main method

public static void main(String[] args)

{

//Create an object for Scanner

Scanner sc = new Scanner(System.in);

//Print the message

System.out.print("Enter an integer of any size: ");

//Get the string from the user

String numberString = sc.nextLine();

//Create an object for the static method

BigInteger bigNum = new BigInteger(numberString);

//Print the output

System.out.println("Factorial of " + bigNum + " is " + factorial(bigNum));

}

//Static method "factorial"

public static BigInteger factorial(BigInteger value)

{

//Check if the value is equal to zero

if (value.equals(BigInteger.ZERO))

//Return 1

return BigInteger.ONE;

//Else

else

/*Call the function recursively to till the result is found*/

return value.multiply(factorial(value.subtract(BigInteger.ONE)));

}

}

Sample Output

Enter an integer of any size:  50

Factorial of 50 is 30414093201713378043612608166064768844377641568960512000000000000