Question

I was reading a Java tutorial and it said:

Abstract classes cannot be instantiated, but they can be subclassed.

what does this mean? I thought one had to instantiate in order to create a subclass? This line has really confused me, any and all help is much appreciated.

Answer 1

Instantiate:

AbstractClass a = new AbstractClass(); //illegal

Subclass:

class ConcreteClass extends AbstractClass { ... }
ConcreteClass c = new ConcreteClass(); //legal

You must create a new class that extends the abstract class, implement all of the abstract methods, and then use that new class.

Note that you can also do this:

class ConcreteClass extends AbstractClass { ... }
AbstractClass a = new ConcreteClass(); //legal