Invoking a method overloaded where all arguments implement the same interface
- by double07
Hello,
My starting point is the following:
- I have a method, transform, which I overloaded to behave differently depending on the type of arguments that are passed in (see transform(A a1, A a2) and transform(A a1, B b) in my example below)
- All these arguments implement the same interface, X
I would like to apply that transform method on various objects all implementing the X interface.
What I came up with was to implement transform(X x1, X x2), which checks for the instance of each object before applying the relevant variant of my transform.
Though it works, the code seems ugly and I am also concerned of the performance overhead for evaluating these various instanceof and casting. Is that transform the best I can do in Java or is there a more elegant and/or efficient way of achieving the same behavior?
Below is a trivial, working example printing out BA. I am looking for examples on how to improve that code. In my real code, I have naturally more implementations of 'transform' and none are trivial like below.
public class A implements X {
}
public class B implements X {
}
interface X {
}
public A transform(A a1, A a2) {
System.out.print("A");
return a2;
}
public A transform(A a1, B b) {
System.out.print("B");
return a1;
}
// Isn't there something better than the code below???
public X transform(X x1, X x2) {
if ((x1 instanceof A) && (x2 instanceof A)) {
return transform((A) x1, (A) x2);
} else if ((x1 instanceof A) && (x2 instanceof B)) {
return transform((A) x1, (B) x2);
} else {
throw new RuntimeException("Transform not implemented for "
+ x1.getClass() + "," + x2.getClass());
}
}
@Test
public void trivial() {
X x1 = new A();
X x2 = new B();
X result = transform(x1, x2);
transform(x1, result);
}
