Reputation: 3415

which .toString is called in this case?

Object aThing = new Integer(25);
aThing.toString();

Is it the toString of the Object or toString of the Integer? (I think it's Integer's.)

Upvotes: 1

Answers (5)

kosa

Reputation: 66657

Integer class toString() will be called. Method invocation will always be decided based on the Object type rather than reference type.

As Steve Kuo commented: except static methods.

Upvotes: 3

Natix

Reputation: 14257

Integer's toString is called. Which method implementation is called is always determined by the runtime type (class) of the object itself, not by the type of the variable it is assigned to. In the following code, both of the calls are equivalent.

Integer i = Integer.valueOf(5);
Object o = i;

i.toString(); // "5"
o.toString(); // "5"

Methods that behave this way are called Virtual Methods. All non-static methods in Java are virtual. They provide one of key mechanisms of Polymorphism.

Upvotes: 1