Java Program to Multiply Large numbers

Java program to multiply large numbers has been shown here. This program follows the standard multiplication algorithm.

Page content(s):

1. Program & Output

1. Java program & output to Multiply Large numbers

Code has been copied

/***************************************
	     alphabetacoder.com
 Java program to multiply large numbers
****************************************/

import java.util.Scanner;

class Main {
    public static void main(String args[]) {
        // declare instance of Scanner class
        Scanner sc = new Scanner(System.in);

        // declare varables
        char[] num1 = new char[500]; // for storing first numbers.
        char[] num2 = new char[500]; // for storing second numbers.
        int[] result = new int[1000]; // for storing the result
        int n1, n2, d1, d2, i, j, sum, carry, flag = 0;

        // Read input numbers
        System.out.print("Enter the first number: ");
        num1 = sc.next().toCharArray();
        System.out.print("Enter the second number: ");
        num2 = sc.next().toCharArray();

        //find the number of digits for both numbers.
        n1 = num1.length;
        n2 = num2.length;

        // Perform multiplication
        // Multiply each digit of num1 with each digit of num2
        for (i = n1 - 1; i >= 0; i--) {
            // initialize
            carry = 0;
            d1 = num1[i] - '0'; // current digit of first number

            for (j = n2 - 1; j >= 0; j--) {
                d2 = num2[j] - '0'; // current digit of second number
                // calculate sum
                sum = d1 * d2 + result[i + j + 1] + carry;
                result[i + j + 1] = sum % 10;
                // calculate carry
                carry = sum / 10;
            }

            // Set the carry to the leading digit
            result[i] = carry;
        }

        // display the result
        // discard the leading 0s in result array
        System.out.print("Result = ");
        for (i = 0; i < (n1 + n2); i++) {
            if (result[i] != 0)
                flag = 1;
            if (flag == 1)
                System.out.print(result[i] + "");
        }
    }
}

Output

Enter the first number: 95645321827654784646846744467874574999555664226577

Enter the second number: 57454545445787798756998862211360065474755258565

Result = 5495258489623991547912527139389052273835545445473793418196901198146636507325023577503884379882005