Abstract Methods and Classes

In java method cannot be redefined in a subclass by making it as final. But the abstract concept is opposite to final.

Abstract can be indicated that a method must always be redefined in a subclass.

The keyword abstract is used for making methods and classes abstract.

Abstract Class

The class which is declared using keyword abstract called as abstract class.

Properties of abstract Class

• When the class is declared as abstract then methods can be declared as abstract.
• It is not neccessary in class that all methods should be abstract.
• When abstract class contains abstract methods then class must be inherited by child class to write the body of the abstract methods.

Abstract Methods

The methods which are declared as abstract called as abstract methods.

Properties of abstract methods

• They are always declared in the parent class.
• All methods which are declared as abstract must be always redefined in all the child classes.
• The class must be abstract in order to declare abstract methods.
• Abstract methods are always declared in the parent class without writting it's body.
• We can declare abstract methods in the subclass too.

Abstract class and method Syntax

abstract class className // abstract class declaration
{                        
    abstract type methodName(); // abstract method declaration
}

Example
                  
Program to demonstrate abstract class and method.
abstract class Software
{
    String name;
    abstract void features();
}
		
Output
I'm display 1
I'm display 2

			

                           		
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