What is Abstract keyword in JAVA? Read About Abstract keyword in JAVA Examples, Interface, Class

Abstract Keyword in JAVA

The abstract keyword is cast off to attain abstraction in Java. It is a non-obtainable catalyst which is used to produce abstract classes and methods.

The title role of an abstract class is to hold the abstract methods. It might also hold non-abstract methods. The method that is announced with an abstract keyword and which doesn't have any execution is called an abstract method. The abstract keyword is a non-obtainable catalyst that is cast off for the classes and the methods.

Abstract class: is a cramped class which can not be used to make objects to access them, it can be elevated from another class.

Abstract method: the abstract method can be cast off in an abstract class, which does not have a body. The body is created by the subclass (elevated from).

Characteristics of Abstract Keyword in Java 

 The abstract keyword in Java is used to explain abstract classes and methods. The characteristics of abstract keywords are listed below:

Abstract classes cannot be instantiated: An abstract class is a class which is unable to be installed straightway. In place of it, this is meant to be enlarged by other classes, which may allow concrete execution of the abstract methods.

Abstract methods do not have a body: An abstract method is a method that does not have an execution . It is explained by the abstract keyword in java and ends with a semicolon ( : ) in place of a method body. Subclasses of an abstract class also allow a concrete execution of all abstract methods explained in the parent class.

Abstract classes can have both abstract and concrete methods: Abstract classes hold both abstract and concrete methods. Concrete methods are executed in the abstract class only, therefore it can be utilized by both the abstract class and the subclasses.

Abstract classes can have constructors: Abstract classes also have constructors, which help in ablation to establish representative variables and perform other established tasks. However, abstract classes might not be incorporated directly, their constructors are originally known as constructors in concrete subclasses.

Abstract classes can contain instance variables: Abstract classes might hold instance variables, which might be used by both the abstract class and its subclasses. It's easier to access Subclasses with these variables directly, likewise to any other instance variables.

Abstract classes can implement interfaces: Abstract classes might discharge interfaces, which explain a set of methods that can be applied by any class that shows the interface. In such a case, the abstract class also allows concrete execution of all methods explained in the interface.

 Rules of Abstract Keyword

Don'ts of Abstract Keyword

• An abstract keyword is unable to be used with variables and constructors.
• If a class is abstract, it is unable to be symbolized.
• If a method is abstract, it cannot hold the body.
• One might not use the abstract keyword with the end goal one.
• One might not explain abstract methods as private.
• It's impossible to explain abstract methods as static.  
• An abstract method is unable to coexist.

Do's of Abstract Keyword

• An abstract keyword can be cast off only with class and method.
• An abstract class can attain constructors and static methods.
• If a class enlarges the abstract class, it must also execute one of the abstract methods.
• An abstract class can hold the lead method and the end method.
• An abstract class can allow abstract methods to be overloaded.
• One can explain the abstract as an inner class.
• One can explain the abstract method with a fling clause.

Why is it Difficult to Create an Object of an Abstract Class?

An abstract class is broadly unexplained. It contains abstract methods that are not executed, not for once. An abstract class originally explains the representation of classes that will receive from it.

• An abstract class has a well-secured constructor (by default),  prevailing only derived types to launch it.

Also, let's assume that we are permitted to build objects of abstract classes. Then, what will happen when one calls an abstract method undergoing those objects? There will be no original execution of the method to supplicate.

• The abstract keyword is a powerful and strong tool for explaining abstract classes and methods in Java. By elaborating a class or method as abstract, developers can allow a structure for subclassing and make sure that certain methods are executed consistently in all of the subclasses.