What is the Math.floorMod method in Java?

floorMod is a static method of the Math class that returns the floor modulus of the two numbers passed to it. The sign of the return value is the same as the sign of the passed divisor.

The formula to calculate floorMod is as follows:

floorMod(dividend, divisor) = dividend - (floorDiv(dividend, divisor) * divisor)

If the dividend and divisor are of the same sign, then the results of floorMod and the normal modulo operation are the same.
If the dividend and divisor are of different signs, then the result of floorMod has the same sign of the divisor.

The relationship between floorMod and floorDiv is as follows:

floorDiv(dividend, divisor) * divisor + floorMod(dividend, divisor) == dividend

The Math.floorMod method is introduced in Java 8.

The floorMod method is defined in the Math class, which is defined in the java.lang package.

To import the Math class, use the statement below:

import java.lang.Math;

Example 1

dividend - 23
divisor - 4

The fractional representation is $23/4$ .

floorDiv(23, 4) = 5
floorMod(23, 4) = 23 - ( 5 * 4 ) = 23 - 20 = 3

Example 2

dividend - -23
divisor - 4

The fractional representation is $-23/4$ .

floorDiv(-23, 4) = -6
floorMod(-23, 4) = -23 - ( -6 * 4 ) = -23 - (-24) = -23 + 24 = 1

Example 3

dividend - 23
divisor - -4

The fractional representation is $23/-4$ .

floorDiv(23, -4) = -6
floorMod(23, -4) = 23 - ( -6 * -4 ) = 23 - 24 = 23 - 24 = -1

Example 4

dividend - -23
divisor - -4

The fractional representation is $-23/-4$ .

floorDiv(-23, -4) = 5
floorMod(-23, -4) = -23 - ( 5 * -4 ) = -23 - (-20) = -23 + 20 = -3

import java.lang.Math;
public class Main{
    public static void main(String[] args){
        int dividend = 23;
        int divisor = 4;
        int remainder = Math.floorMod(dividend, divisor);
        System.out.printf("floorMod(%d, %d) = %d", dividend, divisor, remainder);
        System.out.println();
        dividend = 23;
        divisor = -4;
        remainder = Math.floorMod(dividend, divisor);
        System.out.printf("floorMod(%d, %d) = %d", dividend, divisor, remainder);
        System.out.println();
        dividend = -23;
        divisor = 4;
        remainder = Math.floorMod(dividend, divisor);
        System.out.printf("floorMod(%d, %d) = %d", dividend, divisor, remainder);
        System.out.println();
        dividend = -23;
        divisor = -4;
        remainder = Math.floorMod(dividend, divisor);
        System.out.printf("floorMod(%d, %d) = %d", dividend, divisor, remainder);
        System.out.println();
    }
}