[JAVA][Beginning Java 8 Games Development]

Chapter 10 ■ Directing the Cast of Actors: Creating a Casting Director Engine and Creating the Bagel Actor Class
Often there is a misunderstanding as to the use of this Java modifier keyword final with regard to objects. It is
true that with most Java variables (numeric, Boolean, and String) when made final, the variable value itself can’t be
changed. Many assume that a final modifier when used with a Java object (variable declaration) also makes the object
itself “final,” and therefore “immutable,” or not changeable in memory.
Generally in Java the final keyword when used with an object variable refers to memory references, and the
immutable keyword applies to those objects themselves, and means that they can’t be changed. Therefore, an object
(reference) that is declared as final can still contain an object that is mutable (can be changed, as we wish to do here).
In fact, what the final modifier keyword does regarding Java objects in memory, such as our CURRENT_CAST
ArrayList object, is to make the reference to where it’s being kept in memory locked, that is, finalized. So
what NetBeans is suggesting here is an optimization that will allow your CURRENT_CAST data store object to remain
where it is in memory all of the time (after it is created).
This does not mean that your List ArrayList object itself can’t change. Your game’s Java code can
expand, contract, and clear (reset) a List ArrayList object that has been declared final at any time, based
upon your game’s invocation of the .addCurrentCast(), .removeCurrentCast(), and .resetCurrentCast() methods.
The optimization theory here would be the more a JVM can “lock down” memory locations “up front” (upon
program launch, when loading into memory), the better it can optimize memory, as well as the CPU cycles that are
needed to access this memory. If you think about it, if the CPU does not have to “look” for an object in memory, then
it will be able to access it faster. A final object can also be used more optimally in a multi-threaded environment.
If, however, you do not want to make your object references final, you can optionally turn this feature off in
NetBeans. This can be done using the Tools ➤ Options menu sequence, seen on the left side of Figure 10-6, in order
to access the Options dialog, which is shown in the right side of Figure 10-6. As you can see along the top of this
Options dialog, NetBeans has organized it’s hundreds of preferences (also known as options) into ten specific areas,
and even has a Search Filter, seen at the top right of the dialog as well, in case you don’t know exactly where to look
for a given option. If any of these sections have too many options to display on the dialog screen, there will be tabs
(the hints tab is shown selected in Figure 10-6), which you can use to navigate to an area you want to visit. We’re
going to the Hints section, and selecting the Java Language from the drop-down, and then finally opening up the
Threading section.
Figure 10-6. Setting Editor Hints Preferences using the Tools ➤ Options menu and the Editor ➤ Hints ➤ Java ➤ Threading
Now that we have covered the final object variable issue, and shown you both ways of dealing with it, let’s continue on,
and create a second ArrayList object named COLLIDE_CHECKLIST to store complex collision data.
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