Java Remainder of Integer Divison?

Question

I was searching around about this topic but I still don't get it, if someone can elaborate I would be very thankful.

My task is to divide two variables as integer division with remainder.. The problem is, that I have no clue what a remainder is, for now I did something like that, this is what I found by searching through the internet:

int a;
int b;
int remainder = Math.Pow(a,2) % b;

System.out.println("a^2 / b = " + Math.Pow(a,2) / b);
System.out.println("remainder = " + remainder);

if I for example set (a = 43) and (b = 67)

Then I will get this reslut:

a^2 / b = 27
remainder = 40

Now since I have no idea what the remainder is (this is just a suggestion form the internet) I have no idea if this is the correct answer..?

Thanks for any help,

Kind Regards

Answer 1

If you are looking for the mathematical modulo operation you could use

int x = -22;
int y = 24;
System.out.println(Math.floorMod(x, y));

If you are not interested in the mathematical modulo (just the remainder) then you could use

int x = -22;
int y = 24;
System.out.println(x%y);

Answer 2

    public static void main(String[] args) {
        int dividend = 139, divisor = 7;

        int quotient = dividend / divisor;
        int remainder = dividend % divisor;

        System.out.println("The Quotient is = " + quotient);
        System.out.println("The Remainder is = " + remainder);
    }

Output:

The Quotient is = 19

The Remainder is = 6

Answer 3

Yes, the % operator will return the remainder of the Integer division.

To know more about the remainder of the Integer division check out Wikipedia:

If a and d are integers, with d non-zero, it can be proven that there exist unique integers q and r, such that a = qd + r and 0 ≤ r < |d|. The number q is called the quotient, while r is called the remainder.

Answer 4

int remainder = a % b; will sort you. The remainder operator returns the remainder of the division.

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Note that the remainder operator is also called the modulo operator. However, this is incorrect for Java as Java will return a negative value if the left operand a is negative.

Answer 5

% operator will return the remainder of the Integer division.

What modules actually does under the hood ?

Modules tend to remove cycles from the number, until it reaches a positive number that is smaller than the number of the cycle which we call modulo OR a negative number which we call a reminder.

However, Using % operator is time expensive.

To avoid using % while getting the same result, we can use the following:

• While(a >= n) a -= n; (when a is a positive number)

• While(a < 0) a += n; (when a is a negative number)

• a = n*q + r that means r = a - n*q While q is the integer division of a/n which means a%n == a - n * Math.toIntExact(a/n) Which is sufficient when a is a positive number.

• While a is a negative number, we can use (a%n + n) % n Which will give you module.

Case Scenario on Clock:

if it is now 9 O'clock, what time after 4 hours => 9+4 = 13h => 13%12=1 while 12 is the cycle number in the clock

What if we need to calculate time before 24 hours (Yesterday) from now which is 9 O'clock, then: 24(2*12) => Yesterday Means 9-24 = -15h While the right answer is 9 , to solve this we will use (a%n + n) % n While a%n == (a - n * Math.toIntExact(a/n)) then -15 - 12 * Math.toIntExact(-15/12) = -3 => -3 + 12 = 9 => 9%12 => 9 - 12 * Math.toIntExact(9/12) = 9 Which is the right answer.

This is the code for the clock Scenario:

public static void main(String args[]){
    Scanner scanner = new Scanner(System.in);
    int a = scanner.nextInt(); // a = -15
    int n = scanner.nextInt(); // cycle = 12

    int reminder = a - (n * Math.toIntExact(a / n));
    int reminder_plus_n = (reminder + n);
    int modulo = reminder_plus_n - (n * Math.toIntExact(reminder_plus_n / n));
    System.out.println(modulo); // Answer = 9
}