Java integer division doesn't give floor for negative numbers

java integer floor
AMACB picture AMACB · May 18, 2016 · Viewed 7.1k times · Source

I was trying to use java's integer division, and it supposedly takes the floor. However, it rounds towards zero instead of the floor.

public class Main {
    public static void main(String[] args) {
        System.out.println(-1 / 100); // should be -1, but is 0
        System.out.println(Math.floor(-1d/100d)); // correct
    }
}

The problem is that I do not want to convert to a double/float because it needs to be efficient. I'm trying to solve this with a method, floorDivide(long a, long b). What I have is:

static long floorDivide(long a, long b) {
    if (a < 0) {
        // what do I put here?
    }
    return a / b;
}

How can I do this without a double/float?

Answer

Frank Harper picture Frank Harper · Apr 26, 2017

floorDiv() from Java.Math that does exactly what you want.

static long floorDiv(long x, long y)

Returns the largest (closest to positive infinity) long value that is less than or equal to the algebraic quotient.

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