Inheritance Notes

Creating References usin Inheritance hierarcies

Superclasses and subclasses are generally organized into a single root tree structure called an inheritance hierarchy. In this type of hierarchy, attributes and methods that are associated with a specific class are inherited by lower levels of the hierarchy.
When working with a hierarchy of subclasses and superclasses, the object type and reference type can be different when instantiating an object variable. Example: Fruit fruit1 = new Apple(); In this case, the reference type is declared with the superclass, while the object type is declared with the subclass.

Polymorphism can be used when we have multiple classes that are related by inheritance. It is utilized when a method is implemented to perform different tasks in different classes. It essentially allows a method to take on multiple “forms” or implementations based on the specific object it is acting upon.
Polymorphism is useful for code reusability, as it re-implements an existing class’s attributes and methods for new classes. A real life example of polymorphism could be a sport. A sport can take on different forms, as it can be soccer, basketball, baseball, etc.

The object superclass is located at the top of every class hierarchy. This means all of the other classes in a hierarchy can use the attributes and methods of the object superclass through inheritance. It is a part of the built-in java.lang package.
The object superclass contains common, useful methods such as equals() and toString(). The equals() method compares two objects; it is often used to check for equality between 2 String objects, comparing each character of both strings to check if they are the same.