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

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);
    }
}

Output:

15%2^(1) = 1
15%2^(2) = 3
15%2^(3) = 7

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