Compute modulus division by a power-of-2-number using Wrapper Class

Last Updated : 21 Jun, 2017

Prerequisite : Compute modulus division by a power-of-2-number

Now as you know for getting n modulus 2^k, we just need to return k bits(from LSB) in binary representation of n. In Java, you can use Wrapper class toBinaryString() method to get binary string representation of a number and getting substring from (str.length()-k) to end. And then by using Integer.parseInt(), you can convert this binary substring to number which is the remainder. Below is the Java program to demonstrate the same.

// Java program to Compute modulus 
// division by a power-of-2-number 
  
class Test 
{ 
    // Driver method 
    public static void main(String[] args)  
    { 
        int num = 15; 
          
        int two_power1 = 1; 
        int two_power2 = 2; 
        int two_power3 = 3; 
          
        String binary = Integer.toBinaryString(num); 
        int len = binary.length(); 
          
        String rem1 = binary.substring(len-two_power1); 
        String rem2 = binary.substring(len-two_power2); 
        String rem3 = binary.substring(len-two_power3); 
          
        int reme1 = Integer.parseInt(rem1, 2); 
        int reme2 = Integer.parseInt(rem2, 2); 
        int reme3 = Integer.parseInt(rem3, 2); 
          
        System.out.println(num + "%" + "2^(" + two_power1 + ") = " + reme1); 
        System.out.println(num + "%" + "2^(" + two_power2 + ") = " + reme2); 
        System.out.println(num + "%" + "2^(" + two_power3 + ") = " + reme3); 
    } 
} 