Java Abstract Class And Methods

Abstract classes are similar to interfaces.

Java abstract class and methods. Any class that extends an abstract class must implement all the abstract methods. Any class that contains one or more abstract methods must also be declared abstract. Abstract method can never be final and static. A class containing abstract methods should also be abstract.

To implement features of an abstract class we inherit subclasses from it and create objects of the subclass. We use the abstract keyword to create abstract classes and methods. Abstract class in java with abstract methods and examples. Method that are declared without any body within an abstract class are called abstract method.

You cannot instantiate them and they may contain a mix of methods declared with or without an implementation. Important rules for abstract methods. An abstract class can have abstract and non abstract concrete methods and cant be instantiated with inheritance polymorphism abstraction encapsulation exception handling multithreading io streams networking string regex collection jdbc etc. It is extended by a long list of subclasses concurrenthashmap concurrentskiplistmap enummap hashmap identityhashmap treemap weakhashmap.

The method body will be defined by its subclass. However with abstract classes you can declare fields that are not static and final and define public protected and private concrete methods. Abstract class classname abstract method. An abstract method doesnt have any implementation method body.

A subclass must override all abstract methods of an abstract class. We cannot create objects of an abstract class. With interfaces all fields are automatically public static and final and all methods that you declare or define as default methods are public. These class share and reuse many methods from this abstract class like get put isempty.