Java polymorphism when passing variables.

Question

class X{
    public void print(X x){System.out.println("xx");}
    public void print(Y y){System.out.println("xy");}
}
class Y extends X{
    public void print(X x){System.out.println("yx");}
    public void print(Y y){System.out.println("yy");}

    public static void main(String[] args){
        X x = new Y();
        x.print(x);
        System.out.println(x.getClass());
    }

}

The output i get is "yx" end I dont understand why, x.getClass() returns "class Y" so shouldn't its call the method where the parameter is Y?

Overloading is resolved at compile time (where `x` is an `X`), not runtime. — GriffeyDog, May 24 '18 at 19:39

score 2 · Accepted Answer · answered May 24 '18 at 19:39

2

Overloads (i.e. choice which of multiple methods of the same class/interface with the same name to use) are resolved based on static types. This is in opposition to overriding (choice between X#print(X) and Y#print(X) which is resolved at runtime.

answered May 24 '18 at 19:39

Alexey Romanov

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score 1 · Answer 2 · answered May 24 '18 at 19:41

1

Dynamic binding doesn't work for method parameters, hence parameter resolution of method is done in compile time, and the compiler resolves with the static type X.

answered May 24 '18 at 19:41

NiVeR

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Java polymorphism when passing variables.

2 Answers2