Book Image

Java Fundamentals

By : Gazihan Alankus, Rogério Theodoro de Brito, Basheer Ahamed Fazal, Vinicius Isola, Miles Obare
Book Image

Java Fundamentals

By: Gazihan Alankus, Rogério Theodoro de Brito, Basheer Ahamed Fazal, Vinicius Isola, Miles Obare

Overview of this book

Since its inception, Java has stormed the programming world. Its features and functionalities provide developers with the tools needed to write robust cross-platform applications. Java Fundamentals introduces you to these tools and functionalities that will enable you to create Java programs. The book begins with an introduction to the language, its philosophy, and evolution over time, until the latest release. You'll learn how the javac/java tools work and what Java packages are - the way a Java program is usually organized. Once you are comfortable with this, you'll be introduced to advanced concepts of the language, such as control flow keywords. You'll explore object-oriented programming and the part it plays in making Java what it is. In the concluding chapters, you'll get to grips with classes, typecasting, and interfaces, and understand the use of data structures, arrays, strings, handling exceptions, and creating generics. By the end of this book, you will have learned to write programs, automate tasks, and follow advanced courses on algorithms and data structures or explore more advanced Java courses.
Table of Contents (12 chapters)
Java Fundamentals

Polymorphism and Overriding

The next principle of OOP we will cover is called polymorphism. The term "polymorphism" stems from biology in that an organism can take many forms and stages. This term is also used in OOP in that sub-classes can define their unique behaviors yet still share some functionalities with their parent classes.

Let's illustrate this with an example.

In our Person example, we had a method, walk. In our Student class, which inherits from the Person class, we will redefine the same walk method, but now walking to class instead of just walking. In our Lecturer class, we will also redefine the same walk method and this time walk to the staff room instead of walking to class. This method must have the same signature and return type as the walk method in the superclass for this to be considered polymorphic. Here is what the implementation looks like in our Student class:

public class Student extends Person {
   public void walk(int speed){
       //Walk to class