How to multiply two numbers of any digits in Java

This code is implemented and provided by Himanshu from Agra University.

By using this code we can multiply two numbers of any digits. 

Note : Before using this code please create a Java Project in Eclipse IDE and save this class inside 
MultiplicationOfNumbers.java file.

import java.util.Scanner;

public class MultiplicationOfNumbers {
    public static void main(String args[]) {
   
    Scanner sc = new Scanner(System.in);

    System.out.print("Enter first String in integer format :");
    String num1=sc.next();
 
System.out.print("Enter second String in integer format :");
    String num2=sc.next();
   
    // create two objects of string-builder using the data of
    // 'num1' and 'num2' then reverse it and convert into string,
    //  then store it inside string
    String n1 = new StringBuilder(num1).reverse().toString();
    String n2 = new StringBuilder(num2).reverse().toString();

    int[] d = new int[num1.length()+num2.length()];
    for(int i=0; i<n1.length(); i++){
        for(int j=0; j<n2.length(); j++){
            d[i+j] += (n1.charAt(i)-'0') * (n2.charAt(j)-'0');
        }
    }
   
// create object of string-builder class (it is a muttable object)
// in this object we will store the intermediate calculations
    StringBuilder sb = new StringBuilder();
   
    for(int i=0; i<d.length; i++){
        int mod = d[i]%10;
        int carry = d[i]/10;
        if(i+1<d.length){
            d[i+1] += carry;
        }
        sb.insert(0, mod);
    } 
   
    while(sb.charAt(0) == '0' && sb.length()> 1){
      sb.deleteCharAt(0); 
   }
 
  // convert the string-builder into string and
  // store the result in string
  String result = sb.toString();
  System.out.println("Result of multiplication is "+result);
 
  } // end of main
} // end of class

Output of Code :
Enter first String in integer format :200
Enter second String in integer format :900
Result of multiplication is 180000