Inheritance - is the inclusion of state and behavior of a base class in a derived class so that they are accessible in that derived class. The key benefit of Inheritance is that it gives the formal mechanism for
code reuse. Any shared piece of business logic may be moved from the derived class into the base class as part of refactoring method to improve maintainability of your code by avoiding code duplication. The existing class is called the superclass and the derived class is defined the subclass. Inheritance may also be illustrate as the process whereby one object requires characteristics from one or more other objects the similar way children accepts characteristics from their parents. There are basically two types of inheritances:
1. Implementation inheritance: You will extend an application's functionality by reusing functionality in the parent class by extending all or some of the operations already implemented. In Java, you can only add from one superclass. Implementation inheritance promotes reusability but improper use of class inheritance can gives programming nightmares by dividing encapsulation and building future changes a problem. With implementation inheritance, the subclass becomes hardly coupled with the superclass. This will build the design fragile because if you need to change the superclass, you have to know all the details of the subclasses to avoid breaking them. So when using implementation inheritance, make sure that the subclasses relay only on the nature of the superclass, not on the actual implementation.
2. Interface inheritance: That is also known as subtyping. Interfaces give a mechanism for specifying a relationship between otherwise unrelated classes, typically by specifying a set of common methods each implementing class must obtain. Interface inheritance provides the design concept of program to interfaces not to implementations. This also reduces implementation dependencies or the coupling between systems. In Java, you will implement any number of interfaces. This is more flexible and reliable than implementation inheritance because it won't restrict you into specific implementations which build subclasses difficult to maintain. So care could be taken not to divide the implementing classes by modifying the interfaces.