Android: which operator for modulo (% doesn't work with negative numbers)

Question

If I try

int a=(-2)%6

I get -2 instead of 4.

Why does it behave this way with negative numbers?

Answer 1

% does a remainder operation in Java.

To get a proper modulus, you can use the remainder in a function:

It's shortest using ternary operator to do the sign fixup:

private int mod(int x, int y)
{
    int result = x % y;
    return result < 0? result + y : result;
}

For those who don't like the ternary operator, this is equivalent:

private int mod(int x, int y)
{
    int result = x % y;
    if (result < 0)
        result += y;
    return result;
}

Answer 2

Because if you divides -2 by 6, you will get -2 as remainder. % operator will give the remainder just like below;

int remainder = 7 % 3;  // will give 1
int remainder2 = 6 % 2; // will give 0

To get the modulo:

    // gives m ( mod n )
public int modulo( int m, int n ){
    int mod =  m % n ;
    return ( mod < 0 ) ? mod + n : mod;
}