Mastering Java: The Ultimate Quiz for 'Thinking in Java'

Is it possible to upcast from a derived class to a base class in Java?

1. Casting a base class reference to a derived class

2. Casting a derived class reference to a base class

3. Forcing garbage collection of a derived class object

4. Creating an abstract method in the derived class

The correct answer is: Casting a base class reference to a derived class

Upcasting in Java refers to the act of casting a reference of a base class to a reference of a derived class. This allows for the use of methods and variables that are specific to the derived class. Option B is incorrect because it refers to downcasting instead, which is the opposite of upcasting. Option C is incorrect because garbage collection is not related to upcasting. Option D is incorrect because creating an abstract method is not specific to upcasting.