Abstract Classes and Methods |
In this
lesson we will learn about Abstract Classes and Abstract Methods in Java
programminglangauge.
Abstract Methods
An abstract method is a method that is declared in a (super)class, but not defined. In order to be instantiated, a subclass must provide the definition.
Abstract Classes
An abstract class is any class that includes an abstract method. It is similar to Pure virtual in C++. If a class includes an abstract method, the class must be declared abstract, too.
Code Example:
Abstract Methods
An abstract method is a method that is declared in a (super)class, but not defined. In order to be instantiated, a subclass must provide the definition.
Abstract Classes
An abstract class is any class that includes an abstract method. It is similar to Pure virtual in C++. If a class includes an abstract method, the class must be declared abstract, too.
Code Example:
abstract
class AbstractClass {
abstract public void Print();
// no body, just the function header
}
class
MyConcreteClass extends AbstractClass {
public void Print() {
// actual code goes here
}
}
Important
points to be remembered:
- An abstract class cannot be
instantiated.
- A subclass of an abstract class that
does not provide bodies for all abstract methods must also be declared
abstract.
- A subclass of a non-abstract class can override a
(non-abstract) method of its superclass, and declare it abstract. In that
case, the subclass must be declared abstract.
