[JAVA][Beginning Java 8 Games Development]

Chapter 3 ■ A Java 8 Primer: An Introduction to Java 8 Concepts and Principles
■ ■Note If any of the data fields or methods in the superclass that you are extending (or, if you prefer, subclassing) have
been declared using the private access control keyword, those variables (or constants) and methods are reserved for use
only by (or within) that superclass, and thus will not be accessible to your subclass. The same rules apply to nested and
inner classes; these class structures cannot use any code declared as private in the Java constructs that contain them
(or that are above them, if you will).
The body of your class is coded inside the curly braces (see Figure 3-2, outermost red box), which follow your
class (and javafx.application.Application superclass, in this case) declaration. This is why you learned about Java
syntax first, and you are building on that with the class declaration and the Java syntax that holds the class definition
(variables, constants, methods, constructor, nested classes) constructs.
As you can see in the figure, the InvinciBagel class extends an Application superclass from the JavaFX package.
The inheritance diagram (a tool I will be using throughout the book to show you where things come from in the
overall Java and JavaFX API schemas) for your current superclass-to-subclass hierarchy will therefore look like this:
> java.lang.Object
> javafx.application.Application
> invincibagel.InvinciBagel
By extending the javafx.application package and its Application class, you will give the InvinciBagel class
everything it needs to host (or run) the JavaFX application. The JavaFX Application class “constructs” an Application
object so that it can use system memory; call an .init() method, to initialize anything that may require initializing; and
call a .start() method (see Figure 3-2, second-outermost red box), which puts things into place that will ultimately be
needed to fire up (start) an InvinciBagel Java 8 game application.
When the end user finishes using the InvinciBagel game application, the Application object, created by
the Application class, using the Application() constructor method, will call its .stop() method and remove your
application from system memory, thus freeing up that memory space for other uses by the your end-users. You will
be learning about Java 8 methods, constructors, and objects soon, as you are progressing from the high-level package
and class constructs, to lower-level method and object constructs, and so you are moving from a high-level overview
to lower levels. You may be wondering if Java classes can be nested inside each other, that is, if Java classes contain
other Java classes. The answer is yes, they certainly can (and do)! Let’s take a look at the concept of Java nested
classes next.
Nested Classes: Java Classes Living Inside Other Classes
A nested class in Java is a class that is defined inside of another Java class. A nested class is part of the class in which
it is nested, and this nesting signifies that the two classes are intended to be used together in some fashion. There
are two types of nested classes: static nested classes, which are commonly referred to simply as nested classes, and
nonstatic nested classes, which are commonly referred to as inner classes.
Static nested classes, which I will refer to as nested classes, are used to create utilities for use with the class that
contains them, and are sometimes used only to hold constants for use with that class. Those of you who develop
Android applications are very familiar with nested classes, as they are quite commonly employed in the Android API,
to hold either utility methods or Android constants, which are used to define things such as screen density settings,
animation motion interpolation curve types, alignment constants, and user interface element scaling settings. If you
are looking for an understanding regarding the concept of static, it can be thought of as fixed, or not capable of being
changed. A photograph is a static image, whereas video is not static. We’ll look at this concept often during this book.
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