In this article, we'll be discussing abstract classes in Java and how they can be used in Object Oriented Programming. First, we'll give a brief overview of what an abstract class is. Then, we'll provide a few examples to help illustrate how abstract class works.
What is Abstract Class in Java?
An abstract class is a class that cannot be instantiated, meaning you cannot create new instances of an abstract class. An abstract class can, however, be sub classed. When you subclass an abstract class, you can create new instances of that subclass.
An abstract class is a bit like a template for creating new classes. When you subclass an abstract class, you can add your own implementation details to the subclass.
Syntax of Abstract Class
An abstract class in Java is a class that cannot be instantiated. That means you cannot create new instances of an abstract class using the new operator. An abstract class can have both abstract and non-abstract (concrete) methods.Abstract classes are created so that other classes can inherit from them. The child classes can override the methods of their parent class.
An abstract class must be declared with the keyword abstract. Here is the syntax of an abstract class in Java:
abstract class MyClass {
// fields and methods go here
}
Abstract Class Example
An Abstract class is a class that contains one or more abstract methods. An abstract method is a method that is declared but not implemented in the code. When a class contains an abstract method, the class must also be declared as abstract.
Example:
public abstract class Shape {
public abstract void draw();
}
public class Circle extends Shape {
public void draw() {
// code to draw a circle...
}
}
Concrete Class
The class which implements all the methods of an abstract class is called a concrete class.
If you're just getting started with object-oriented programming in Java, you're probably wondering what an abstract class is. Simply put, an abstract class is a class that can't be instantiated - meaning you can't create new objects of that type. However, you can create subclasses (also called child classes) that inherit from an abstract class. So while you can't create new objects of the abstract class type, you can create new objects of the subclass type.
Why would you want to create an abstract class? There are two main reasons:
1. To provide a template for creating subclasses
2. To prevent someone from accidentally creating an object of the wrong type
Let's say you have a superclass called Animal and two subclasses called Dog and Cat. If Animal is an abstract class, then no one can accidentally create an Animal object - they would have to specifically create a Dog or Cat object. This is important because if someone did accidentally create an Animal object, they might try to call methods that only make sense for Dogs or Cats - and that could cause errors in your program.
Creating an Abstract Class in Java
Creating an abstract class in Java is pretty easy - just
Can all Classes be Abstract In Java?
No, all classes cannot be abstract in Java. However, any class can be declared abstract by using the keyword abstract. An abstract class is a class that is usually used as a base class from which other classes can inherit. An abstract class cannot be instantiated, meaning you cannot create an object of that type. A class that is declared as abstract must provide the implementation for all of its non-abstract methods.
Use of Abstract Class
An abstract class is a type of class that cannot be instantiated. That means you cannot create new instances of an abstract class. However, you can create a new instance of a concrete class that extends the abstract class.
The purpose of an abstract class is to provide a template for other concrete classes to extend. An abstract class can contain both abstract and concrete methods. A concrete method is a method with a body that contains code. An abstract method is a method without a body.
If you want to use an abstract class, you need to extend it and then override the abstract methods in the child class. If you don't override the abstract methods, your program will not compile.