Job Ready Java

Lesson 20Diving into Inheritance

In this part of our lesson, we will look at specialization and inheritance. In Lesson 17, we discussed how inheritance can be used to model an is-a relationship between objects. These relationships are hierarchical in nature and express a true inheritance, or parent-child, relationship between objects. In this lesson, we will cover extension of classes, method overloading, method overriding, access control, and how polymorphism works with inheritance.

As mentioned earlier in this lesson, you won't explicitly use inheritance often in the rest of this course or in web application development, but you will implicitly use inheritance all the time. Inheritance is a foundational concept of object-oriented programming, and you must have a good understanding of this concept to be a successful object-oriented developer.

LEARNING OBJECTIVES

By the end of this lesson, you will be able to:

• Explain how everything extends object
• Explain what a parent class is, including synonyms
• Explain what a child class is, including synonyms
• Use access control to extend objects
• Explain is-a versus has-a relationships
• Discuss the benefits of a well-designed inheritance hierarchy
• Reuse code with inheritance
• Overload a method
• Explain the use of constructors with derived and base classes
• Use polymorphism with inheritance
• Relate an abstract base class to a base class and an interface

EVERYTHING EXTENDS OBJECT

The Object class is the parent of every class in Java; ...