Multiply 2 numbers using recursion

In many interviews, interviewer may asked to write a simple program to multiply 2 integers without using '*' operator. We can solve this program by many ways like using looping, recursion, bitwise operator etc.,

In this tutorial we will see how to multiply 2 integers using recursion. As simple as method takes 1st (n) and 2nd (m) integer as argument and make recursive call m times. Each time summing with n and returning the final sum.

Lets see simple example to multiply 2 integers using recursion.

public class MultiplyNumber {

 public static void main(String[] args) {
  
  int val = new MultiplyNumber().multiply(7, 5);
  System.out.println(val);
 }
 
 public int multiply(int n, int m) {
  if(m>n) {
   int tmp = n;
   n = m;
   m = tmp;
  }
  return multiply(n,m,0);
 }
 
 public int multiply(int n, int m,int val) {
  if(m <= 0) return val;
  return multiply(n,m-1,val+n);
 }
}

OUTPUT:

35