[JAVA][Beginning Java 8 Games Development]

Chapter 3 ■ A Java 8 Primer: An Introduction to Java 8 Concepts and Principles
■ ■Note It is possible to use, instead of the Java import keyword, the fully qualified class name, that is, to preface the
class name with the package name, right inside your Java code. Convention dictates using the import statement; however,
line 20 in Figure 3-2 could be written as javafx.scene.control.Button btn = new javafx.scene.control.
Button(); if you wanted to buck standard Java programming convention.
Java Classes: Logical Java Constructs to Build On
The next logical Java programming construct beneath the package level is the Java class level, as you saw in the import
statement, which references both the package that contains the class and a class itself. Just as a package organizes all
the related classes, so too a class organizes all its related methods, variables, and constants and, sometimes, other
nested classes.
Thus, the Java class is used to organize your Java code at the next logical level of functional organization, and so
your class will contain Java code constructs that add functionality to your application. These may include methods,
variables, constants, nested classes, or inner classes.
Java classes can also be used to create Java objects. Java objects are constructed, using your Java class, and have
the same name as the Java class and as that class’s constructor method.
As you saw in Figure 3-2, you declare your class, using a Java class keyword, along with a name for your class. You
can also preface the declaration with Java modifier keywords, which you will be studying later in this chapter (see the
section “Java Modifier Keywords: Access Control and More”). Java modifier keywords are always placed before (or in
front of) the Java class keyword, using the following format:
class
One of the powerful features of Java classes is that they can be used to modularize your Java game code so
that your core game application features can be a part of a high-level class that can be subclassed to create more
specialized versions of that class. Once a class has been subclassed, it becomes a superclass, in Java class hierarchy
terminology. A class will always subclass a superclass using a Java extends keyword. If a class does not extend a given
superclass in this way, then it automatically extends the Java masterclass: java.lang.Object. This is so that every class
in Java can create an object by implementing a constructor method.
Using a Java extends keyword tells the compiler that you want the superclass’s capabilities and functionality
added (extended) to your class, which, once it uses this extends keyword, becomes a subclass. A subclass extends the
core functionality that is provided by the superclass. To extend your class definition to include a superclass, you add to
(or extend, no pun intended) your existing class declaration, using the following format:
class extends
When you extend a superclass with your class, which is now a subclass of that superclass, you can use all the
superclass’s features (nested classes, inner classes, methods, variables, constants) in your subclass, without having
them all explicitly written (coded) in the body of your class, which would be redundant (and disorganized).
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