One of the core ideas of object-oriented programming is inheritance, which enables the development of new classes based on preexisting classes. Either an abstract class or an interface can be used in Java to implement inheritance. Both of these techniques offer a means of defining a group of shared properties and methods that can be used by several classes.
A class that cannot be directly instantiated is known as an abstract class, and it is frequently used to specify a set of common properties and methods that should be implemented by its subclasses. Subclasses must implement all of the abstract methods specified in an abstract class, and abstract classes may have both concrete and abstract methods.
On the other hand, interfaces offer a means to specify a set of methods that every class that implements the interface must implement. A set of method signatures are defined by an interface, but no implementation information is included. Every method specified in an interface must have an implementation in any class that implements the interface.
A class can implement several interfaces, but it can only derive from one abstract class when it comes to inheritance with interfaces and abstract classes. This is due to Java’s capability for multiple inheritance of interfaces but not multiple inheritance of classes.
By extending several interfaces, Java interfaces can also be utilised to create a type of multiple inheritance. The methods and properties defined in each interface can be inherited by a class that implements several interfaces.
On the other side, abstract classes can be utilised to offer a foundation implementation for a group of related classes. By doing so, you may lessen code duplication and make sure that all classes that are connected have the same set of attributes and methods.
In conclusion, Java programming is fundamentally based on inheritance with interface and abstract classes. While abstract classes offer a way to establish a common set of attributes and methods that can be shared by numerous classes, interfaces offer a way to specify a set of methods that must be implemented by any class that implements the interface. Developers can choose when to use each of these two methods in their Java applications by being aware of the distinctions between them.