Title: Key Concept - Abstract classes and methods
Course: CPS 189: Java Certification - Review, Practice & Prepare (Development) > Section: Learning Modules

An abstract class is a class that cannot be instantiated but can be subclassed.

An abstract class may or may not include abstract methods.  If a class has any abstract methods, it must be declared abstract.

An abstract class contains the keyword abstract in its declaration.

When an abstract class is subclassed, the subclass can define implementations for all of the abstract methods in the superclass.  If it does not, then the subclass must also be declared abstract.

A concrete method is a method that is declared with an implementation (curly braces enclosing statements, followed by a semicolon).

An abstract method is a method that is declared without an implementation.

An abstract method contains the keyword abstract in its declaration.

For additional study, view resources under:

- Level 1 Study Materials: Unit 9
- Level 1 Study Materials: Unit 10