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Do subclasses have to implement interface?
No. An interface defines how a class should look like (as a bare minimum). Whether you implement this in a base class or in the lowest subclass doesn’t matter.
What is an aggregated class?
An aggregate class is a class with no user-declared constructors, no private or protected non-static data members, no base classes, and no virtual functions. Such a class can be initialized with a brace-enclosed comma-separated list of initializer-clauses.
Can classes be subclasses of each other?
In the Java language, classes can be derived from other classes, thereby inheriting fields and methods from those classes. Definitions: A class that is derived from another class is called a subclass (also a derived class, extended class, or child class).
Why do you need to implement all the methods of an interface in class?
It is used to provide total abstraction. That means all the methods in an interface are declared with an empty body and are public and all fields are public, static and final by default. A class that implements an interface must implement all the methods declared in the interface.
How do you aggregate a class?
A class is an aggregate if:
- All of its data members are public.
- It does not define any constructors.
- It has no in-class initializers.
- It has no base classes or virtual functions.
What is aggregation and its types?
Aggregation is a specialized form of association between two or more objects in which each object has its own life cycle but there exists an ownership as well. An essential property of an aggregation relationship is that the whole or parent (i.e. the owner) can exist without the part or child and vice versa.
How are interfaces implemented in a subclass in Java?
The interface has to be entirely implemented throughout the hierarchy of sub classes and base class and has to be defined at the level where the interface implementation signature is located ( implements Interface ). The sub classes themselves have no knowledge about the interface, but they have the implicit connection trough their base class.
Can a subclass inherit an interface from an abstract class?
Abstract classes can allow to implement the methods from an interface they implement to be implemented in sub classes by marking the definition as abstract. And as you can see in the main method, both defining the object as BaseClass or SomeInterface works and makes no difference. Thanks for contributing an answer to Stack Overflow!
What does an interface look like in Java?
An interface defines how a class should look like (as a bare minimum). Whether you implement this in a base class or in the lowest subclass doesn’t matter.