How to determine an object's class (in Java) ?

Question

If class B and class C extend class A and I have an object of type B or C, how can I determine which it instantiates?

Answer 1

Use Object.getClass(). It returns the runtime type of the object.

Answer 2

if (obj instanceof C) {
//your code
}

Answer 3

You can use:

Object instance = new SomeClass();
instance.getClass().getName(); //will return the name (as String) (== "SomeClass")
instance.getClass(); //will return the SomeClass' Class object

HTH. But I think most of the time it is no good practice to use that for control flow or something similar...

Answer 4

Any use of any of the methods suggested is considered a code smell which is based in a bad OO design.

If your design is good, you should not find yourself needing to use getClass() or instanceof.

Any of the suggested methods will do, but just something to keep in mind, design-wise.

Answer 5

there is also a .isInstance method on the "Class" class. if you get an objects class via myBanana.getClass() you can see if your object myApple is an instance of the same class as myBanana via

myBanana.getClass().isInstance(myApple)