Java abstract class fields

Constructor in Java Abstract Class. Constructor is always called by its class name in a class itself . A constructor is used to initialize an object not to build the object. As we all know abstract classes also do have a constructor.

We define an abstract class with the abstract modifier preceding the class keyword . An abstract class can be subclassed, but it can’t be instantiated. If a class defines one or more abstract methods, then the class itself must be declared abstract. An abstract class can declare both abstract and concrete methods.3 May 2020

Abstract classes cannot be instantiated , but they can be subclassed. When an abstract class is subclassed, the subclass usually provides implementations for all of the abstract methods in its parent class. However, if it does not, then the subclass must also be declared abstract .

We can’t use @Autowired on a constructor of an abstract class. Spring doesn’t evaluate the @Autowired annotation on a constructor of an abstract class. The subclass should provide the necessary arguments to the super constructor.