Type of Inheritance

Single Inheritance
Multilevel Inheritance
Hierarchical Inheritance
Multiple Inheritance
Hybrid Inheritance

1. Single Inheritance

In single inheritance, a single subclass extends from a single superclass. For example,

Example:

class Animal{  
void eat()
{
System.out.println("eating...");
}  
} 
class Dog extends Animal
{  
void bark()
{
System.out.println("barking...");
}  
public static void main(String args[]){  
Dog d=new Dog();  
d.bark();  
d.eat();  
}
}

Output:

barking…
eating…

2. Multilevel Inheritance

In multilevel inheritance, a subclass extends from a superclass and then the same subclass acts as a superclass for another class. For example,

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

Output:

weeping…
barking…
eating…

3. Hierarchical Inheritance

In hierarchical inheritance, multiple subclasses extend from a single superclass. For example,

4. Multiple Inheritance

In multiple inheritance, a single subclass extends from multiple superclasses. For example,

Note: Java doesn’t support multiple inheritance. However, we can achieve multiple inheritance using interfaces [TBD]

5. Hybrid Inheritance

Hybrid inheritance is a combination of two or more types of inheritance. Here, we have combined hierarchical and multiple inheritance to form a hybrid inheritance.

Difference Between this and this() in Java

this keyword is used to refer to the current object, i.e. through which the method is called.
this() is used to call one constructor from the other of the same class.