[JAVA][Beginning Java 8 Games Development]

Chapter 3 ■ A Java 8 Primer: An Introduction to Java 8 Concepts and Principles
A class that has been declared using the abstract modifier keyword cannot be instanced, and it is intended to be
used as a superclass (blueprint) to create (extend) other classes. Because a final class cannot be extended, you will not
use the final and abstract modifier keywords together at the class level. If a class contains any methods that have been
declared using the abstract modifier keyword, the class must itself be declared an abstract class. An abstract class does
not have to contain any abstract methods, however.
A method that has been declared using the abstract modifier keyword is a method that has been declared for
use in subclasses but that has no current implementation. This means that it will have no Java code inside its method
body, which, as you know, is delineated in Java by using curly braces. Any subclass that extends an abstract class
must implement all these abstract methods, unless the subclass is also declared abstract, in which case the abstract
methods are passed down to the next subclass level.
Java’s Volatile Modifier: Advanced Multithreading Control over Data Fields
The Java volatile modifier keyword is used when you are developing multithreaded applications, which you are not
going to be doing in basic game development, as you want to optimize your game well enough so that it only uses one
thread. The volatile modifier tells the Java virtual machine (JVM), which is running your application, to merge the
private (that thread’s) copy of the data field (variable or constant) that has been declared volatile with the master copy
of that variable in system memory.
This is similar to the static modifier keyword, the difference being that a static variable (data field) is shared by
more than one object instance, whereas a volatile data field (variable or constant) is shared by more than one thread.
Java’s Synchronized Modifier: Advanced Multithreading Control over Methods
The Java synchronized modifier keyword is also used when you are developing multithreaded applications, which
you are not going to be doing for your basic game development here. The synchronized modifier tells the JVM, which
is running your application, that the method that has been declared synchronized can be accessed by only one thread
at a time. This concept is similar to that of synchronized database access, which prevents record access collisions.
A synchronized modifier keyword likewise prevents collisions between threads accessing your method (in system
memory) by serializing the access to one at a time so that parallel (simultaneous) access to a method in memory by
multiple threads will never occur.
Now that you have studied primary Java constructs (classes, methods, and fields) and basic modifier keywords
(public, private, protected, static, final, abstract, and so on), let’s journey inside the curly braces now, learning about
the tools that are used to create the Java programming logic that will eventually define your game app’s game play.
Java Data Types: Defining Data Type in Applications
Because you have already learned about variables and constants encountered in a few of Java’s data types, let’s explore
these next, as it is not too advanced for your current progression from easy to more difficult topics!
There are two primary data type classifications in Java: primitive data types, which are the ones that you are the
most familiar with if you have used a different programming language, and reference (object) data types, which you
will know about if you have used another OOP language, such as Lisp, Python, Objective-C, C++, or C# (C Sharp).
Primitive Data Types: Characters, Numbers, and Boolean (Flags)
There are eight primitive data types in the Java programming language, as shown in Table 3-1. You will be using
these as you work your way through the book to create your InvinciBagel game, so I am not going to go into detail
regarding each one of them now, except to say that Java boolean data variables are used for flags or switches (on/off),
char is used for Unicode characters or to create String objects (an array of char), and the rest are used to hold numeric
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