Book Image

Java 9 with JShell

By : Gaston C. Hillar
Book Image

Java 9 with JShell

By: Gaston C. Hillar

Overview of this book

The release of Java 9 has brought many subtle and not-so-subtle changes to the way in which Java programmers approach their code. The most important ones are definitely the availability of a REPL, known as JShell, which will make experiments and prototyping much more straightforward than the old IDE-based project-led approach. Another, more subtle change can be seen in the module system, which will lead to more modularized, maintainable code. The techniques to take full advantage of object-oriented code, functional programming and the new modularity features in Java 9 form the main subjects of this book. Each chapter will add to the full picture of Java 9 programming starting out with classes and instances and ending with generics and modularity in Java.
Table of Contents (23 chapters)
Java 9 with JShell
Credits
About the Author
Acknowledgement
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface
Index

Generating classes to create objects


Imagine that we have to draw and calculate the perimeters and areas of three different rectangles. You will end up with three rectangles drawn with their widths and height values and their calculated perimeters and areas. It would be great to have a blueprint to simplify the process of drawing each rectangle with their different width and height values.

In object-oriented programming, a class is a template definition or blueprint from which objects are created. Classes are models that define the state and behavior of an object. After declaring a class that defines the state and behavior of a rectangle, we can use it to generate objects that represent the state and behavior of each real-world rectangle.

Note

Objects are also known as instances. For example, we can say each rectangle object is an instance of the Rectangle class.

The following picture shows two rectangle instances named rectangle1 and rectangle2. These instances are drawn with their width and...