Glossary
Diamond problem
A problem that arises in programming languages supporting multiple inheritance, where a class inherits from two parent classes that both inherit from a common grandparent class. This creates ambiguity when a method defined in the grandparent is overridden in both parent classes, making it unclear which version the inheriting class should use.
Example:
If Shape is a grandparent, and Circle and Square are parents inheriting from Shape (each with a draw() method), a class ColoredShape trying to inherit from both Circle and Square would face the diamond problem regarding which draw() method to use.
Inheritance
A fundamental principle in object-oriented programming where a new class (subclass) can acquire the properties and behaviors (methods and instance variables) of an existing class (superclass). This promotes code reusability and establishes an 'is-a' relationship.
Example:
In a game, a Knight class might inherit from a Character class, automatically gaining basic attributes like health and attack power.
Subclass
A class that derives from another class (the superclass), inheriting its methods and instance variables. It can also introduce its own unique methods and variables, making it a more specific type of the superclass.
Example:
If Vehicle is a superclass, then Motorcycle would be a subclass, inheriting general vehicle properties but adding specific motorcycle features like hasSidecar.
Superclass
A class whose properties and behaviors are inherited by one or more other classes (subclasses). It represents a more general or broader category from which more specific classes are derived.
Example:
In a hierarchy of electronic devices, Appliance could be a superclass for Refrigerator and Toaster, providing common traits like powerConsumption.
extends keyword
A Java keyword used in a class declaration to specify that the class being declared is a subclass of another class. It establishes the inheritance relationship, allowing the subclass to inherit members from the superclass.
Example:
To make a Cat class inherit from an Animal class, you would declare public class Cat **extends** Animal { ... }.