Abstract Classes

An abstract class is a class that cannot be instantiated on its own. It serves as a blueprint for other classes and provides common functionality that can be inherited by its subclasses. An abstract class may contain both implemented and abstract methods.

To declare an abstract class in Java, you use the abstract keyword in the class definition. Here’s an example:

public abstract class Animal {
    // instance variables

    // constructor(s)

    // implemented methods

    // abstract method(s)
}

#Java #AbstractClasses

Concrete Classes

On the other hand, a concrete class is a class that can be instantiated directly. It provides a specific implementation of the abstract methods declared in its abstract superclass. Concrete classes can also have their own unique properties and methods.

Here’s an example of a concrete class that extends the abstract class Animal:

public class Dog extends Animal {
    // instance variables

    // constructor(s)

    // implemented methods

    // additional methods
}

#Java #ConcreteClasses

Key Differences

The main difference between abstract classes and concrete classes is that abstract classes cannot be instantiated, while concrete classes can. Abstract classes serve as a way to define a common interface and shared functionality for a group of related classes, while concrete classes provide specific implementations.

Another important distinction is that concrete classes must provide implementations for all the abstract methods declared in their abstract superclass. Failure to do so will result in a compilation error.

When to Use Abstract Classes and Concrete Classes?

• Use abstract classes when you want to provide a common interface and shared functionality to a group of related classes, and when you want to enforce that certain methods should be implemented by subclasses.
• Use concrete classes when you want to provide specific implementations and allow them to be instantiated directly.

In conclusion, abstract classes and concrete classes play different roles in Java programming. Abstract classes provide a blueprint for other classes and cannot be directly instantiated, while concrete classes can be instantiated and provide specific implementations. By understanding the difference and using them appropriately, you can write more modular and flexible code in your Java applications.