[JAVA][Beginning Java 8 Games Development]

Chapter 3 ■ A Java 8 Primer: An Introduction to Java 8 Concepts and Principles
As you can see at the bottom of Figure 3-2, for the .main() method, created by NetBeans for your InvinciBagel
class definition, which uses the public modifier, you can use more than one Java modifier keyword. The .main()
method first uses a public modifier keyword, which is an access control modifier keyword, and then a static modifier
keyword, which is a nonaccess control modifier keyword.
Access Control Modifiers: Public, Protected, Private, Package Private
Let’s cover access control modifiers first, because they are declared first, before nonaccess modifier keywords or
return type keywords, and because they are easier to understand conceptually. There are four access control modifier
levels that are applied to any Java code structure. If you do not declare an access control modifier keyword, a default
access control level of package private will be applied to that code structure, which allows it to be visible, and thus
usable, to any Java programming structure inside your Java package (in this case, invincibagel).
The other three access control modifier levels have their own access control modifier keywords, including public,
private, and protected. These are somewhat aptly named for what they do, so you probably have a good idea of how
to apply them to either share your code publicly or protect it from public usage, but let’s cover each one in detail
here, just to make sure, as access (security) is an important issue these days, inside your code as well as in the outside
world. I will start with the least amount of access control first!
Java’s Public Modifier: Allowing Access by the Public to Java Program Constructs
The Java public access modifier keyword can be used by classes, methods, constructors, data fields (variables and
constants), and interfaces. If you declare something public, it can be accessed by the public! This means that it can be
imported and used by any other class, in any other package, in the entire world. Essentially, your code can be used in
any software that is created using the Java programming language. As you will see in the classes that you use from the
Java or JavaFX programming platforms (APIs), the public keyword is most often used in open-source programming
Java platforms or packages that are employed to create custom applications, such as games.
It is important to note that if a public class that you are trying to access and use exists in a package other than your
own (in your case, invincibagel), then the Java programming convention is to use the Java import keyword to create an
import statement that allows use of that public class. This is why, by the time you reach the end of this book, you will
have dozens of import statements at the top of your InvinciBagel.java class, as you will be leveraging preexisting Java
and JavaFX classes in code libraries that have already been coded, tested, refined, and made public, using the public
access control modifier keyword, so that you can create Java 8 games with them to your heart’s content!
Owing to the concept of class inheritance in Java, all the public methods and public variables inside a public
class will be inherited by the subclasses of that class (which, once it is subclassed, becomes a superclass). Figure 3-2
offers an example of a public access control modifier keyword, in front of the InvinciBagel class keyword.
Java’s Protected Modifier: Variables and Methods Allow Access by Subclass
The Java protected access modifier keyword can be used by data fields (variables and constants) and by methods,
including constructor methods, but cannot be used by classes or interfaces. The protected keyword allows variables,
methods, and constructors in a superclass to be accessed only by subclasses of that superclass in other packages (such
as the invincibagel package) or by any class within the same package as the class containing those protected members
(Java constructs).
This access modifier keyword essentially protects methods and variables in a class that is intended to be (hoped
to be used as) a superclass by being subclassed (extended) by other developers. Unless you own the package that
contains these protected Java constructs (which you do not), you must extend the superclass and create your own
subclass from that superclass to be able to use the protected methods.
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