Java: get greatest common divisor

Question

I have seen that such a function exists for BigInteger, i.e. BigInteger#gcd. Are there other functions in Java which also works for other types (int, long or Integer)? It seems this would make sense as java.lang.Math.gcd (with all kinds of overloads) but it is not there. Is it somewhere else?

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(Don't confuse this question with "how do I implement this myself", please!)

Answer 1

For int and long, as primitives, not really. For Integer, it is possible someone wrote one.

Given that BigInteger is a (mathematical/functional) superset of int, Integer, long, and Long, if you need to use these types, convert them to a BigInteger, do the GCD, and convert the result back.

private static int gcdThing(int a, int b) {
    BigInteger b1 = new BigInteger(""+a); // there's a better way to do this. I forget.
    BigInteger b2 = new BigInteger(""+b);
    BigInteger gcd = b1.gcd(b2);
    return gcd.intValue();
}

Answer 2

public int GCD(int a, int b)
{
   if (b==0) return a;
   return GCD(b,a%b);
}

Answer 3

Or the Euclidean algorithm for calculating the GCD...

public int egcd(int a, int b) {
    if (a == 0)
        return b;

    while (b != 0) {
        if (a > b)
            a = a - b;
        else
            b = b - a;
    }

    return a;
}

Answer 4

Because no one has really answered the original question yet:

No, there is no such function in Java.