Inheritance in Java with example programs

Inheritance:

In Java, here classes can be reused in several ways, this is done by creating new classes, reusing the properties of the existing class. This mechanism of deriving a new class from an old one that is called Inheritance. The inheritance allows sub-classes to inherit all the variables and methods of their parent classes.

Types of Inheritance in Java:

There are four types of inheritance are exists:

Single Inheritance:

In Single Inheritance, having only one superclass and one subclass. The subclass inherits all the properties and behaviours only from a single class.

In Fig: class A serves as a base class for the derived class B.

Program:

class rectangle
{
 int length;
 int breadth;
rectangle(int p, int q)
{
 length=p;
 breadth=q;
}
int area()
{
 return(length*breadth);
}
}
class cuboid extends rectangle
{
 int height;
 cuboid(int p, int q, int r)
{
 super(p,q)
 height=r;
}
int volume()
{
 return(length*breadth*height);
}
}
class test
{
 public static void main(String args[])
{
 cuboid c1=new cuboid(15,10,8);
 int area1=rect.area();
 int volume1=rect1.volume();
 System.out.println("The Area of Rectangle:"+area1);
 System.out.println("The Volume of Cuboid:"+volume1);
}
}

Output:

The Area of Rectangle: 150
The Volume of Cuboid: 1200

Hierarchical Inheritance:

In Hierarchical Inheritance, having one superclass and many subclasses. It supports the hierarchical design of a program.

In fig: class A serves as the base class for the derived class B, class C, class D.

Program:

class P {
    int a = 25;
}
class Q extends P {
 void display() {
        System.out.println("The value of a into Q class is:" + a);
    }
}
class R extends P {
 void display() {
        System.out.println("The value of a into R class is:" + a);
    }
public static void main(String args[]) 
{
        Q q1 = new Q();
        q1.display();
        R r1 = new R();
        r1.display();
    }
}

Output:

The value of a into Q class is:25
The value of a into R class is:25

Multi-level Inheritance:

Java supports Multi-level inheritance concept and uses it extensively in building its class library. It allows us to build a chain of classes.

In Fig: Class A serves as a base class for the derived class B which in turn serves as a base class for the derived class C.

Program:

class Car{
   public Car()
   {
	System.out.println("Car is moving");
   }
   public void vehicleType()
   {
	System.out.println("Vehicle Type: Car");
   }
}
class Bike extends Car{
   public Bike()
   {
	System.out.println("Bike is moving");
   }
   public void brand()
   {
	System.out.println("Brand: KTM");
   }
   public void speed()
   {
	System.out.println("Max Speed: 240Kmph");
   }
}
class Scooty extends Bike{
public Scooty()
   {
	System.out.println("Scooty is moving");
   }
   public void speed()
   {
	System.out.println("Max Speed: 120Kmph");
   }
   public static void main(String args[])
   {
	 Scooty sc=new Scooty();
	 sc.vehicleType();
	 sc.brand();
	 sc.speed();
   }
}

Output:

Car is moving
Bike is moving
Scooty is moving
Vehicle Type: Car
Brand: KTM
Max Speed: 120 Kmph

Multiple Inheritance

In multiple inheritances, having only one subclass and many superclasses. A subclass inherits from more than one immediate superclass.

Program:

class A 
{ 
 void display() 
 { 
    System.out.println("Hello World!"); 
  } 
} 
class B 
{ 
  void display()  
  { 
     System.out.println("Welcome to Webeduclick!"); 
  } 
 } 
class C extends A,B
{ 
 public static void main(String args[]) 
 { 
   C c1 = new C(); 
   c1.display();
  } 
 }

Note: In Java, it doesn’t implement the Multiple Inheritance.

Hybrid Inheritance:

Hybrid inheritance is a combination of single and multiple inheritances.

Program:

public class A 
{
    public void displayA()
    {
        System.out.println("Class A");
    }
}
public class B extends A 
{
    public void show()
    {
        System.out.println("Class B");
    }
    public void displayB()
    {
        System.out.println("Method of Class B");
    }
}
public class C extends A
{
    public void show()
    {
        System.out.println("Class C");
    }
    public void displayC()
    {
        System.out.println(" Method of Class C");
    }
}
public class D extends B, C
{
    public void displayD()
    {
        System.out.println("Method of Class D");
    }
    public static void main(String args[])
    {
          D d1 = new D();
          d1.displayD();
          d1.show();
    }
}