Modulo Operator

Part of the Fundamentals section of Coddy's Java journey — lesson 16 of 73.

The modulo operator % gives the remainder of a division. In Java, it's used with a simple syntax:

result = dividend % divisor;

dividend: The number being divided.
divisor: The number that divides the dividend.
result: The remainder of the division.

For example:

result = 10 % 3;

Here, 10 is divided by 3. 3 goes into 10 three times, with a remainder of 1. So, result will be 1.

What if the dividend is smaller than the divisor? In that case, the divisor goes in 0 times, so the remainder is simply the dividend itself. For example, 2 % 3 equals 2, because 3 goes into 2 zero times with 2 left over.

Usually modulo is used for checking if a number is even or odd:

If a number is even, dividing it by 2 will leave a remainder of 0.
If a number is odd, dividing it by 2 will leave a remainder of 1.

When using modulo with floating-point numbers (doubles), it works similarly to integers but keeps the decimal precision. For example:

double result = 5.2 % 2.0;
// result is 1.2

Here's how it works: 2.0 goes into 5.2 two times (4.0), and the remainder is 1.2 (5.2 - 4.0 = 1.2).

Another example:

double result = 7.8 % 3.5;
// result is 0.8

Challenge

Beginner

Write a code that initializes three variables, a (int), b (double) and c (int) with the values 9, 2.6, and 11 (respectively).

After that, initialize the following variables:

d (int) that will hold the result of a modulo 2
e (int) that will hold the result of a modulo 3
f (double) that will hold the result of b modulo 1.5
g (double) that will hold the result of b modulo 3.9
h (int) that will hold the result of c modulo 10

Check out the result and see how different dividends and divisors affect the result.

Cheat sheet

The modulo operator % gives the remainder of a division:

result = dividend % divisor;

Example with integers:

result = 10 % 3; // result is 1

Common use case - checking if a number is even or odd:

Even numbers: number % 2 == 0
Odd numbers: number % 2 == 1

Modulo with floating-point numbers:

double result = 5.2 % 2.0; // result is 1.2
double result = 7.8 % 3.5; // result is 0.8

Try it yourself

public class Main {
    public static void main(String[] args) {
        // Type your code below
        
        
        // Don't change the line below
        System.out.println("a = " + a);
        System.out.println("b = " + b);
        System.out.println("c = " + c);
        System.out.println("d = " + d);
        System.out.println("e = " + e);
        System.out.println("f = " + f);
        System.out.println("g = " + g);
        System.out.println("h = " + h);
    }
}