variable-length arguments ambiguities

[M Berg]

Hi experts,

my class has a method "test" overloaded few times.
The compiler favours method with double type variable-length arguments (d) over int type (c).
It seems that the simplest possible variable-length call with int types is ambiguous...confusing.
Is there some basic or general rule around why this happens?
Or is this just a variable-length method specialty?

public class Tester {

    public static int test(int value) {//a
        return 0;
    }
    public static double test(double value) {//b
        return 0;
    }

    public static int test(int... value) {//c NEVER here!
        return 0;
    }
    public static double test(double... value) {//d
        return 0;
    }

    public static Object test(Object... values) {
        for (Object o : values) {
            Integer i = null;
            if (o instanceof Integer) {
                i = (Integer) o;
            }
        }
        return 0;
    }

    public static void main(String[] args) {

        int i1 = 1;
        int i2 = 2;
        test(i1);	//ok, goes to a
        //test(i1, i2); //not-good, is ambiguous...??

        Integer I1 = 1;
        Integer I2 = 2;
        test(I1);	//ok, goes to a
        //test(I1, I2); //not-good, is ambiguous...??

        double d1 = 1;
        double d2 = 2;
        test(d1);	//ok, goes to b
        test(d1, d2);	//ok, goes to d

        Object o1 = new Integer(i1);
        Object o2 = new Integer(i2);
        test(o1, o2);
    }
}    

Many thanks again,
Kind regards MB

[Wouter Oet]

I would advise you to read this topic. Just let us know if you still don't get it after that.

[M Berg]

Ok, thanks I missed that one. Found this rule 4b:

4. Combination of the following overloaded methods will result in compiler error:
a. Var-args (V) of primitive type same as argument primitive type
b. Widening + Var-args (WV)
c. Boxing/Unboxing + Var-args (BV)

But just what part of my code exactly breaks or violetes this rule 4b: is it 1) my overloaded methods or 2) my method calls?!
The compiler says only my method call is ambiguous, actual methods seem fine for compiler.

Many thanks
Kind regards MB

[Wouter Oet]

Your method calls make it ambiguous. Ambiguous just means that the compiler doesn't know which method to call because multiple methods match the signature.
If you change your method call to this it works:

test((double)i1, (double)i2); //good