Inheritance in Java | Example

→ Inheritance is an important concepts of OOPs(Object Oriented Programming).

→ Inheritance represents the IS-A relationship which is also known as a parent-child relationship.

→ Inheritance inherit the features(fields and methods) of one class to another class.

→ Inherit the properties of a class use of extends keyword .

→ Inheritance is a mechanism in which one object acquires all the properties and behaviors of a parent object.

Syntax:

    class Super {
          .....
          .....
   }
  class Sub extends Super {
          .....
          .....
}

Important Terminology:

Super Class or Parent Class:- It is also called a base class . The class whose features are inherited is known as super class(or a base class or a parent class).
Sub Class or Child Class:- The class that inherits the another class is known as sub class(or a derived class, extended class, or child class).

Example:

  class Animal
    {
    // eat() method
    // sleep() method
     }
class Dog extends Animal
           {
    // bark() method
}

See in fig....

Full Example 1:

    class Student{  
       int rollno=1122514036;
 }  
 class Teacher extends Student{  
      String course="Eng";
  }
  class StEx{
    public static void main(String args[]){  
     Teacher t=new Teacher();  
      System.out.println("Student Roll No is:"+t.rollno);  
      System.out.println("Teacher  is:"+t.course);  
} 
}  

Types of inheritance in java

→ Threre are Three types of inheritance supported.

Single Inheritance
Multilevel Inheritance
Hierarchical Inheritance

√NOTE: Multiple inheritance and Hybrid Inheritance is not supported in java

1) Single Inheritance

→ A class inherits another class, it is known as a single inheritance.

Example :

    class Animal {
      public void eat() {
      System.out.println("I can eat");  }
    public void sleep() {
      System.out.println("I can sleep");
   }}
class Dog extends Animal {
   public void bark() {
      System.out.println("I can bark");
   }}
   class InheriEx {
   public static void main(String[] args) {
      Dog dog1 = new Dog();
      dog1.eat();
      dog1.sleep();
      dog1.bark();
   }}

Output

2) Multilevel Inheritance

→ There is a chain of inheritance, it is known as multilevel inheritance.

Example :

  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 MultilevelEx{  
public static void main(String args[]){  
BabyDog d=new BabyDog();  
d.weep();  
d.bark();  
d.eat();  
}}  

Output

3) Hierarchical Inheritance

→ When two or more classes inherits a single class.

Example :

 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 HierarchicalEx{  
public static void main(String args[]){  
Cat c=new Cat();  
c.meow();  
c.eat();  
//c.bark();//C.T.Error  
}}  

Output

Q.) Why multiple inheritance is not supported in java?

→ To reduce the complexity and simplify the language, see a scenario example where A, B, and C are three classes. The C class inherits A and B classes. If A and B classes have the same method and you call it from child class object, there will be ambiguity to call the method of A or B class.

Example :

class A{  
void msg(){System.out.println("Hello");}  
}  
class B{  
void msg(){System.out.println("Welcome");}  
}  
class C extends A,B{//suppose if it were  
   
 public static void main(String args[]){  
   C obj=new C();  
   obj.msg();//Now which msg() method would be invoked?  
}  
}  

Output

  Compile Time Error

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OOPs Concepts

Inheritance in Java | Example

Important Terminology:

Types of inheritance in java

1) Single Inheritance

2) Multilevel Inheritance

3) Hierarchical Inheritance

Q.) Why multiple inheritance is not supported in java?