An abstract class in Java is a class that is declared with the abstract keyword. It may contain both abstract and non-abstract methods. Abstract classes cannot be instantiated, meaning you cannot create objects of an abstract class directly. Instead, they are meant to be subclassed by other classes. When an abstract class is subclassed, the subclass usually provides implementations for all the abstract methods in its parent class. However, if it does not, then the subclass must also be declared abstract. Abstract classes are used to achieve data abstraction, which is the process of hiding certain details and showing only essential information to the user. This concept allows you to focus on what an object does rather than how it does it. Abstract classes are similar to interfaces, but they can also contain fields that are not static and final, and define public, protected, and private concrete methods, which interfaces cannot do.
In summary, an abstract class in Java:
- Is declared with the
abstractkeyword. - Can contain both abstract and non-abstract methods.
- Cannot be instantiated and must be subclassed to be used.
- Is used to achieve data abstraction by hiding certain details and showing only essential information to the user.
Abstract classes are an important concept in Java programming, providing a way to define a common interface for a set of subclasses while allowing for some level of implementation flexibility.
