Groovy - can a method defined in an Interface have default values?

Question

If the following is entered in Eclipse/STS (with groovy):

interface iFaceWithAnIssue {
    def thisIsFine(a,b,c)
    def thisHasProblems(alpha='va')
}

The only line that complains is the one trying to use a default value. I can not tell from the codehaus site if this is supported or not.

The IDE error is:

Groovy:Cannot specify default value for method parameter 

So this makes me think it is not supported. As there will be multiple implementations, I wanted to use an interface here. I don't really need the default value in the interface, but there is an error trying to fulfill the interface contract if the implementation class then tries to default this argument. Is there any way?

Answer 1

No, you cannot.

When you define a default value, Groovy actually creates multiple methods in your class, so for example:

class Test {
    void something( a=false ) {
        println a
    }
}

Actually creates

public void something(java.lang.Object a) {
    this.println(a)
}

and

public void something() {
    this.something(((false) as java.lang.Object))
}

This can't be done as it stands in Interfaces.

You could do:

interface iFaceWithAnIssue {
    def thisHasProblems()
    def thisHasProblems(alpha)
}

Then

class Test implements iFaceWithAnIssue {
    // This covers both Inteface methods
    def thisHasProblems(alpha='va') {
        // do something
    }
}