The document discusses inheritance in Java. It defines inheritance as deriving a new class from an existing class, known as the base or parent class. The new class is called the subclass or child class. The subclass inherits all variables and methods from the parent class. There are three types of inheritance in Java: single inheritance where one subclass extends one superclass, multilevel inheritance where a subclass extends another subclass which extends a superclass, and hierarchical inheritance where a superclass has multiple subclasses.

1. By
VINOTH R
St.Joseph’s college(Arts & Science)
Kovur, Chennai

2. • The mechanism of deriving a new class from an old
class is called inheritance.
• The old class is known as the Base class or Parent
class
• The new class is called the Sub class or Derived class
or Child class.
• The inheritance allows subclasses to inherit all the
variables and methods of their parent classes.

3. • Syntax
• The extends keyword indicates that making a
new class that derives from an existing class.
class Subclass-name extends Superclass-name
{
//methods and fields
}

4. As displayed in the figure
• Programmer is the subclass and Employee is the superclass.
• Relationship between two classes is Programmer IS-A
Employee.
• It means that Programmer is a type of Employee.

5. class Employee
{
float salary=40000;
}
class Programmer extends Employee
{
int bonus=10000;
public static void main(String args[])
{
Programmer p=new Programmer();
System.out.println("Programmer salary is:"+p.salary);
System.out.println("Bonus of Programmer is:"+p.bonus);
} }
OUTPUT: Programmer salary is:40000.0
Bonus of programmer is:10000

6. • On the basis of class, there can be three types of
inheritance in java
1. Single
2. Multilevel
3. Hierarchical
• Multiple and hybrid inheritance is supported through
interface only (Will see in Unit 3).

7. • One sub class is derived from one super class
• From the below diagram class A serves as a Super class or
parent class
• Class B serves as a Base class or Sub class.

8. class Animal
{
void eat()
{
System.out.println("eating...");
} }
class Dog extends Animal
{
void bark()
{
System.out.println("barking...");
} }
Class Dog inherits the properties of
Class Animal.
class TestInheritance
{
public static void main(String args[])
{
Dog d=new Dog();
d.bark();
d.eat();
}}
OUTPUT:
barking...
eating...
Animal
Void eat()
Dog
Void bark()
Void eat()

9. • In Multilevel inheritance there is a concept of grandparent
class.
• From the Below diagram then class C inherits class B and
class B inherits class A
• Which means B is a parent class of C and A is a parent class
of B.
• So in this case class C is implicitly inheriting the properties
and method of class A along with B that’s what is called
multilevel inheritance.

10. class Animal
{
void eat()
{
System.out.println("eating...");
}}
class Dog extends Animal
{
void bark()
{
System.out.println("barking...");
}}
class BabyDog extends Dog
{
void weep()
{
System.out.println("weeping...");
}}
class TestInheritance2
{
public static void main(String args[])
{
BabyDog d=new BabyDog();
d.weep();
d.bark();
d.eat();
}}
Output:
weeping...
barking...
eating...
Animal
Void eat()
Dog
Void bark()
Void eat()
BabyDog
void weep()
void bark()
Void eat()

11. • A class has more than one child classes (sub classes).
• More than one child classes have the same parent
class.
• Class A is a parent class of class B and class C and
class C.

12. class Animal
{
void eat()
{
System.out.println("eating...");
} }
class Dog extends Animal
{
void bark()
{
System.out.println("barking...");
} }
class Cat extends Animal
{
void meow()
{
System.out.println("meowing...");
} }
class TestInheritance3
{
public static void main(String args[])
{
Cat c=new Cat();
c.meow();
c.eat();
}}
Output:
meowing...
eating...