Java Math floorMod() Method

The Math.floorMod() is a built-in math function in Java that returns the floor modulus of the integer arguments passed to it. Therefore, floor modulus is (a - (floorDiv(a, b) * b)), has the same sign as the divisor b, and is in the range of -abs(b) < result < +abs(b). The relationship between floorDiv() and floorMod() is:

floorDiv(a, b) * b + floorMod(a, b) == a

The difference in results between floorMod and the % operator is due to the difference between floorDiv() which returns the integer less than or equal to the quotient, and the "/ " operator that returns the integer closest to zero.

Syntax of floorMod() Method

public static int floorMod(int a, int b)

public static long floorMod(long a, long b)

• Parameters:
  • a: the dividend (number to be divided)
  • b: the divisor
• Return Value: It returns the remainder after division, where the result always carries the sign of the divisor
• Exception: If the divisor is 0, it throws an ArithmeticException.

Examples of Java Math floorMod() Method

Example 1: In this example, we are going see how floorMod() method handles different sign cases.

Result 1: 0
Result 2: 23
Result 3: -27
Result 4: 27

Explanation: In this example,

• In the first case, we start with 25 mod 5 and for this, the remainder is 0.
• In the second case, we use 123 mod 50. So, 123 / 50 = 2 with a remainder of 23.
• In the third case, we use 123 mod -50. This returns -27 because it follows the negative sign of the divisor.
• In the fourth example, we use -123 mod 50. The result is 27 because it follows the divisor's sign.

Example 2: In this example, we will perform the division by zero case.

Output:

Exception in thread "main" java.lang.ArithmeticException: / by zero

Explanation: In this example, we try to divide 200 by 0, which is not allowed in Java. So the output of the program throws an ArithmeticException.

When to Use floorMod() Instead of %

We should use floorMod() when:

• We want the result to match the sign of the divisor.
• We are dealing with negative numbers and want consistent behavior.
• We are implementing modular arithmetic such as clock or calendar calculations.