Can you explain the differences between abstract classes and interfaces in Java, and in what scenarios would you use each?

Understanding the Differences between Abstract Classes and Interfaces in Java

Abstract classes and interfaces are both essential components in Java programming, serving different purposes and used in various scenarios. Let's delve into the distinctions between the two:

Abstract Classes:

An abstract class in Java is a class that cannot be instantiated on its own and may contain abstract methods (methods without implementation). Here are some key points about abstract classes:

• Abstract classes can have both abstract and concrete methods.
• They can also have instance variables.
• Subclasses extend abstract classes using the 'extends' keyword.
• Abstract classes are used to define a common base for a group of classes.
• The focus keyword in Java for abstract class is "abstract class".

Interfaces:

An interface in Java is a completely abstract class that defines a set of methods that a class must implement if it implements that interface. Here are some key points about interfaces:

• Interfaces can only have abstract methods with no implementation.
• They cannot have instance variables.
• Classes implement interfaces using the 'implements' keyword.
• Interfaces are used to achieve abstraction and multiple inheritance in Java.
• The focus keyword in Java for interfaces is "interface".

Scenarios for Usage:

Deciding between using an abstract class or an interface depends on the design and requirements of your application. Here are some scenarios to consider:

• Use an abstract class when you want to provide a common base implementation for subclasses.
• Use interfaces when you want to define a contract that must be implemented by multiple classes.
• If a class can inherit only one abstract class but implement multiple interfaces, prioritize using interfaces.
• Interfaces are suitable for establishing common behavior across unrelated classes.

In conclusion, abstract classes and interfaces are powerful tools in Java programming, each serving distinct purposes in software design. By understanding their differences and knowing when to use each, you can effectively structure your code for optimal functionality and maintainability.