Abstract Class & Abstract Method in Core Java

Abstract Class & Abstract Method in Core Java

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  ABSTRACT CLASS MOHIT AGARWAL– (161080107026)
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  INTRODUCTION • “Abstraction” isa process of hiding the implementation details and showing only functionality to the user. • It shows only essential things to the user and hides the internal details. • There are two ways to achieve abstraction in java 1) Abstract class (0 to 100%) 2) Interface (100%)
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  ABSTRACT CLASS &METHOD • An abstract class is a class that is declared ”abstract” it may or may not include abstract methods. • A method which is declared as “abstract” and does not have implementation is known as an abstract method. • Syntax : modifier abstract class className { abstract dataType methodName(); } modifier class childClass extends className { dataType methodName(){} }
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  • An abstractclass must be declared with an abstract keyword. • It can have abstract and non-abstract methods. • It cannot be instantiated. • It can have constructors and static methods also. • It can have final methods which will force the subclass not to change the body of the method. • Any class which contains an abstract method must also be abstract. POINTS TO REMEMBER
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  abstract class Animal//Abstract Class Declaration { public abstract void sound(); //Abstract Method Declaration } public class Dog extends Animal //Dog inherits from Animal { public void sound() { System.out.println("Woof"); } public static void main(String args[]) { Animal obj = new Dog(); obj.sound(); } } OUTPUT : Woof
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  abstract class MyClass { publicvoid disp() { System.out.println("Concrete method of parent class"); } abstract public void disp2(); } class Demo extends MyClass { public void disp2() { System.out.println("overriding abstract method"); } public static void main(String args[]) { Demo obj = new Demo(); obj.disp2(); } } OUTPUT : overriding abstract method
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  • To sharecode among several closely related classes. • If classes that extend your abstract class have many common methods or fields or require access modifiers other than public (such as protected and private). • You want to declare non-static or non-final fields. This enables you to define methods that can access and modify the state of the object to which they belong. USE OF ABSTRACT CLASS