As far as I know, there isn’t any built-in method for primitives. But something as simple as this should do the trick:
public int gcd(int a, int b) {
if (b==0) return a;
return gcd(b,a%b);
}
You can also one-line it if you’re into that sort of thing:
public int gcd(int a, int b) { return b==0 ? a : gcd(b, a%b); }
It should be noted that there is absolutely no difference between the two as they compile to the same byte code.