[JAVA][Beginning Java 8 Games Development]

Chapter 10 ■ Directing the Cast of Actors: Creating a Casting Director Engine and Creating the Bagel Actor Class
This class is a member of the Java Collections Framework, as you might have surmised, as a List, as well as an
Array, both contain collections of data, much like a data structure (or a data store) does, only in a simpler format.
An ArrayList class can “implement” or support the following Java Interfaces: Serializable, Cloneable, Iterable,
Collection, List, and RandomAccess. We will be using the List or, in our case, List Java interface,
which we will be looking at in the next section on List when we will learn about Java Interfaces.
Essentially the ArrayList class (and object) creates a resizable Array implementation of the List interface. An
ArrayList object thus implements all optional List operations, and permits all types of List elements, including null. In
addition to implementing the List Java interface, this class also provides method calls, including a .removeAll(),
.addAll(), and .clear(), which we will be using in our class, to manipulate both the List content as well as the size of the
ArrayList object that is used internally to store the List of Actors (for List) or Images (for List) used.
Each ArrayList object instance has a capacity. The capacity is the size of the Array used to store the elements
(objects) in the List implementation: in our case, a List. The capacity will always be at least as large as the
List size. As elements (Actor objects) are added to an ArrayList, its capacity will grow automatically, which makes it
perfect for our CastingDirector class, as we can make levels of the game more and more complex that is, it can utilize
more Actor objects in the ArrayList of List.
It is important to note that the List implementation is not synchronized (capable of running on multiple
threads simultaneously). If you need to have multiple threads access an ArrayList instance concurrently (at the same
exact time), and at least one of these multiple threads modifies your List structure, it must be synchronized
externally (manually, using your code). We are going to call the CastingDirector class specifically when an enemy is
killed, or a projectile is shot, or a treasure is found (collected) and will not have it being continually called on a pulse.
A structural modification of an ArrayList object is an operation that adds or removes one or more elements;
merely setting the value of an element (Actor) in the ArrayList would not be considered to be structural modification.
The Java Interface: Defining Rules for Implementing Your Class
Before we look at the List Java interface, let’s take a look at what Java interfaces do in general, as we did not have
enough pages to cover all of the Java programming language back in Chapter 3. So I am going to cover some of the
more advanced Java topics as we need to learn them during the book. A good example of this is lambda expressions
in Chapter 9 and Java interfaces here in Chapter 10. The reason for using a Java interface is to make sure that other
programmers who are going to use your code implement it correctly; that is, include everything necessary for the code
to work properly.
Essentially, all an interface specifies is the group of related methods that is needed for another developer to
implement your class. These are specified with “empty method” code bodies. If you wanted to have other developers
use the Hero class, for instance, you would specify a Hero interface. This would be done using the following Java code:
public interface Hero {
public void update();
public boolean collide(Actor actor);
}
As you can see, this is similar to what we did with the .update() method in the Actor superclass, as there is no
{code body} specified as there usually is in a method. Thus, in a sense, a Java interface is also used in an abstract
fashion to define what needs to be included in a class that “implements” the Java interface. As you probably have
guessed, you would thus use the Java implements keyword in your class declaration to implement a Java interface.
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