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Inheritance Understand

Kartik Chandra Mandal February 04, 2020

Inheritance Understand with inner class and inner static class

Inheritance is a fundamental concept in object-oriented programming (OOP). It allows a new class (called a subclass or derived class) to inherit properties and behaviors (methods) from an existing class (called a superclass or base class). Here’s a breakdown of key aspects of inheritance:

  1. Reusability: Inheritance promotes code reusability. You can create a new class by extending an existing class, thus reusing fields and methods of the parent class.
  2. Hierarchy: It helps in establishing a hierarchical relationship between classes. For instance, a Dog class can inherit from an Animal class, establishing that a dog is a type of animal.
  3. Method Overriding: A subclass can provide a specific implementation of a method that is already defined in its superclass. This is known as method overriding.
  4. Polymorphism: Inheritance supports polymorphism, which allows objects to be treated as instances of their parent class rather than their actual class. This enables one interface to be used for a general class of actions.
  5. Single Inheritance vs. Multiple Inheritance:

Ø  Single Inheritance: A class inherits from one superclass. This is the most common form of inheritance.

__________________1

I am static A

I am static B

I am static C

I am static F

I am {} A

I am parameterised constructor A

I am {} B

I am constructor B

I am {} C

__________________2

I am function A

__________________3

30

__________________4

I am {} A

I am parameterised A

__________________5

10

__________________6

20

__________________7

50

__________________8

I am {} A

I am parameterised constructor A

I am {} B

I am constructor B

I am {} C

__________________9

__________________10

I am function C.D

__________________11

I am {} A

I am parameterised constructor A

I am {} B

I am constructor B

__________________12

60

__________________13

 

class A {

 int i = 10;

 static {

  System.out.println("I am static A");

 }

 {

  System.out.println("I am {} A");

 }

 

 public A() {

  System.out.println("I am parameterised A");

 }

 

 public A(int i) {

  this.i = i + 20;

  System.out.println("I am parameterised constructor A");

 }

 

 void function() {

 System.out.println("I am function A");

 }

}

 

class B extends A {

 static int i = 10;

 static {

  System.out.println("I am static B");

 }

 {

  System.out.println("I am {} B");

 }

 

 public B() {

  super(i);

  System.out.println("I am constructor B");

 }

}

class C extends B{

 

  static class D

     {

   static int i=50;

     }

     class E

     {

      B b=new B();

     

     }

    

     static

     {

      System.out.println("I am static C");

     }

     {

      System.out.println("I am {} C");

     }

     C(){

      i = i + 10;

     }

}

class F extends C{

 

 class H extends D

    {

  void function()

     {

   System.out.println("I am function C.D");

     }

    }

    class G extends E

    {

     int i = 60;

     public G(){

      super();

     }

    

    }

   

    static

    {

     System.out.println("I am static F");

    }

}

 

public class Source{

    public static void main(String[] args)

    {

        System.out.println("__________________1");

        A a = new F();

        System.out.println("__________________2");

        a.function();

        System.out.println("__________________3");

        System.out.println(a.i);

        System.out.println("__________________4");

        a=new A();

        System.out.println("__________________5");

        System.out.println(a.i);

        System.out.println("__________________6");

        System.out.println(B.i);

        System.out.println("__________________7");

        System.out.println(C.D.i);

       

        System.out.println("__________________8");

        F f=new F();

        System.out.println("__________________9");

        F.H b=f.new H();

        System.out.println("__________________10");

        b.function();

        System.out.println("__________________11");

        F.G c=f.new G();//this is inner non static class call

        System.out.println("__________________12");

        System.out.println(c.i);

        System.out.println("__________________13");

    }

}

 

 

__________________1

I am static A

I am static B

I am static C

I am static F

I am {} A

I am parameterised constructor A

I am {} B

I am constructor B

I am {} C

__________________2

I am function A

__________________3

30

__________________4

I am {} A

I am parameterised A

__________________5

10

__________________6

20

__________________7

50

__________________8

I am {} A

I am parameterised constructor A

I am {} B

I am constructor B

I am {} C

__________________9

__________________10

I am function C.D

__________________11

I am {} A

I am parameterised constructor A

I am {} B

I am constructor B

__________________12

60

__________________13

 

 

 

Sequence is ---> static block -->simple block --->

 

 

 

 

class A {

 int i = 10;

 static {

  System.out.println("I am static A");

 }

 {

  System.out.println("I am {} A");

 }

 

 public A() {

  System.out.println("I am parameterised A");

 }

 

 public A(int i) {

  //Constructor incrementing static variable or simple variable

  this.i = i + 20;

  System.out.println("I am parameterised constructor A");

 }

 

 void function() {

  System.out.println("I am function A");

 }

 

int a; //initialized to zero

static int b; //initialized to zero only when class is loaded not for each object created.

 

  A(String x,String y){

   //Constructor incrementing static variable b

   b++;

  }

 

   public void showData(){

      System.out.println("Value of a = "+a);

      System.out.println("Value of b = "+b);

   }

  

 

 

}

class B extends A {

 static int i = 10;

 static {

  System.out.println("I am static B");

 }

 {

  System.out.println("I am {} B");

 }

 

 public B() {

  super(i);

  System.out.println("I am constructor B");

 }

}

class C extends B{

 

  static class D

     {

   static int i=50;

     }

     class E

     {

      B b=new B();

     

     }

    

     static

     {

      System.out.println("I am static C");

     }

     {

      System.out.println("I am {} C");

     }

     C(){

      i = i + 10;

     }

}

class F extends C{

 

 class H extends D

    {

  void function()

     {

   System.out.println("I am function C.D");

     }

    }

    class G extends E

    {

     int i = 60;

     public G(){

      super();

     }

    

    }

   

    static

    {

     System.out.println("I am static F");

    }

}

 

public class Source{

    public static void main(String[] args)

    {

        System.out.println("__________________1");

  //this will print first static block and next with out static block from A to F

        A a = new F();

        System.out.println("__________________2");

        a.function();

        System.out.println("__________________3");

        System.out.println(a.i);

        System.out.println("__________________4");

        a=new A();

        System.out.println("__________________5");

        System.out.println(a.i);

        System.out.println("__________________6");

        System.out.println(B.i);

        System.out.println("__________________7");

        System.out.println(C.D.i);

       

        System.out.println("__________________8");

        F f=new F();

        System.out.println("__________________9");

  //this is inner non static class call

        F.H b=f.new H();

        System.out.println("__________________10");

        b.function();

        System.out.println("__________________11");

  //this is inner non static class call

        F.G c=f.new G();

        System.out.println("__________________12");

        System.out.println(c.i);

        System.out.println("__________________13");

  // static inner class declaration

  C.D innerTwo=new C.D(); 

  System.out.println(innerTwo.i);

  // this is inner super class with parameterised argument pass

  B b1=new B();

  C c1=new C(b1);

  System.out.println(c1.a.i);

 

    }

}

 

 

 

 

Ø  Multiple Inheritance: A class can inherit from more than one superclass. Some languages like Python support this, while others like Java do not (instead, Java uses interfaces to achieve similar functionality).

Example in Python:

python

# Base class

class Animal:

    def __init__(self, name):

        self.name = name

 

    def speak(self):

        raise NotImplementedError("Subclass must implement abstract method")

 

# Derived class

class Dog(Animal):

    def speak(self):

        return f"{self.name} says Woof!"

 

class Cat(Animal):

    def speak(self):

        return f"{self.name} says Meow!"

 

# Creating objects

dog = Dog("Buddy")

cat = Cat("Whiskers")

 

print(dog.speak())  # Output: Buddy says Woof!

print(cat.speak())  # Output: Whiskers says Meow!

 

In this example:

Ø  Animal is the base class with an abstract method speak.

Ø  Dog and Cat are derived classes that inherit from Animal and provide their own implementation of the speak method.

Ø  When speak is called on instances of Dog and Cat, the overridden method in the respective subclass is executed.

Benefits of Inheritance:

Ø  Code Maintenance: It makes code easier to maintain and modify.

Ø  Logical Grouping: It helps in logically grouping related classes, which makes the code more readable and organized.

Drawbacks of Inheritance:

Ø  Complexity: Deep inheritance hierarchies can lead to increased complexity.

Ø  Tight Coupling: Subclasses are tightly coupled with their superclasses, which can reduce flexibility.

Understanding and effectively using inheritance can lead to more robust and maintainable code in object-oriented programming.

 

Inheritance Understand
Inheritance Understand




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