Description
Introduction
For this assignment you are to extend your game from Assignment #1 (A1) to incorporate
several important design patterns, and a Graphical User Interface (GUI). The rest of the game
will appear to the user to be similar to the one in A1, and most of the code from A1 will be
reused, although it will require some modification and reorganization.
An important goal for this assignment will be to reorganize your code so that it follows the
Model-View-Controller (MVC) architecture. If you followed the structure specified in A1, you
should already have a “controller”: the Game class containing the play() method. The
GameWorld class becomes the “data model”, containing the collection of game objects and
other game state information. You are also required to add two classes acting as “views”: a
score view which will be graphical, and a map view which for now will retain the text-based
form generated by the ‘m’ command in A1 (in A3 we will replace the text-based map with an
interactive graphical map).
Single-character commands entered via a text field in A1 will be replaced by GUI
components (side menu items, buttons, key bindings, etc.). Each such component will have an
associated “command” object, and the command objects will perform the same operations as
previously performed by the single-character commands.
The program must use appropriate interfaces and build-in classes for organizing the
required design patterns. The following design patterns are to be implemented in this
assignment:
• Observer/Observable – to coordinate changes in the model with the various views,
• Iterator – to walk through all the game objects when necessary,
• Command – to encapsulate the various commands the player can invoke,
• Strategy – to control movement for additional (non-player) robots.
• Singleton – to ensure that only a single instance of player robot can exist.
Model Organization
GameWorld is to be reorganized so that it has a GameObjectCollection which
contains a collection of game objects. All game objects are to be contained in this single
collection. Any routine that needs to process the objects in the collection must access the
collection via an iterator (described below).
The model is also to contain the same game state data as A1 (current clock time and
lives remaining), plus a new state value: a flag indicating whether Sound is ON or OFF
(described below).
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Views
A1 contained two functions to output game information: the ‘m’ key for outputting a “map”
of the game objects in the GameWorld, and the ‘d’ key for outputting current game/playerrobot state data (i.e., the number of lives left, the current clock value, last base number the
player’s robot has reached sequentially so far, the player robot’s current energy level, and
player robot’s current damage level). Each of these two operations is to be implemented in this
assignment as a view of the GameWorld model. To do that, you will need to implement two
new classes: a MapView class containing code to output the map, and a ScoreView class
containing code to output the current game/player-robot state information.
To implement this, GameWorld should be defined as an observable, with two
observers– MapView and ScoreView. Each of these should be “registered” as an observer
of GameWorld. When the controller invokes a method in GameWorld that causes a change in
the world (such as a game object moving, or a new energy station being added to the world)
the GameWorld notifies its observers that the world has changed. Each observer then
automatically produces a new output view of the data it is observing – the game world objects
in the case of MapView, and a description of the game/player-robot state values in the case of
ScoreView. The MapView output for this assignment is unchanged from A1: text output on
the console showing all game objects which exist in the world. However, the ScoreView is to
present a graphical display of the game/player-robot state values (described in more detail
below).
Recall that there are two approaches which can be used to implement the Observer
pattern: defining your own IObservable interface, or extending the build-in CN1
Observable class. You are required to use the latter approach (where your GameWorld
class extends java.util.Observable) and the tips for it are given at the end of the handout.
Note that you are also required to use the build-in CN1 Observer interface (which also
resides in java.util package).
In order for a view (observer) to produce the new output, it will need access to some of
the data in the model. This access is provided by passing to the observer’s update() method
a parameter that is a reference back to the model (which is done automatically by the
notifyObservers() built-in method when built-in Observable class is used). Note this
has the undesirable side-effect that the view has access to the model’s mutators, and hence
could modify model data (later in the lectures, we will discuss how to address this issue with
the Proxy pattern).
Non-Player Robots (NPRs)
The “game object” hierarchy will be the same as in A1 except that you will add a new kind
of movable object called NonPlayerRobot, which extends from Robot. The game
initialization code should create and add to the game world three instances of
NonPlayerRobot (so that there are now four robots – the player’s robot which is an instance
of Robot plus three “Non-Player Robots (NPRs)”. Each NPR is to have an initial location
which is “near” the first base, but not exactly at the first base; instead, each NPR should be at
least several robot lengths away from the first base (this is to make sure that the NPRs are not
colliding with the player’s robot to start with).
When an NPR collides with the player’s robot, the player’s robot sustains damage just as
described in A1 – including that if the robot sustains so much damage that it can no longer
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move the player loses a life, and the world is reinitialized. NPRs also sustain damage when
they collide, but you should initialize them with much higher values so that they can compete
longer (consider NPRs to be “armored” so that they can sustain more damage).
NPRs will be controlled by separate pieces of code called strategies which can be altered
using a new “Change Strategies” command; this is described under “Strategy Pattern”, below.
Having NPRs in this version of the game introduces an additional case for ending the
game such that if a NPR reaches the last base before the player does, the game will end with
the following message displayed on the console: “Game over, a non-player robot wins!”.
GUI Operations
Game class extends Form (as in A1) representing the top-level container of the GUI. The
form should be divided into five areas: one for “score” information, three for commands, and
one for the “map” (which will be an empty container for now but in subsequent assignments
will be used to display the map in graphical form). See the sample picture at the end. Note that
since user input is via GUI components, flow of control will now be event-driven and there is
no longer any need to invoke the play() method – once the Game is constructed it simply
waits for user-generated input events. Note however that it is still a requirement to have a
“Starter” class as described in A1.
Hence, in this assignment, the play() method used in A1 which prompts for singlecharacter commands and reads them from a text field on the form is to be discarded. In its
place, commands will be input through three different mechanisms: on-screen buttons, key
bindings, and side menu items (we will also utilize a tile bar area item to provide help as
explained below). Each command will be invokable via a combination of these mechanisms.
You are to create command objects (see below) for each of the commands from A1 (except
“d” and “m” which are implemented as views in A2, and “y” and “n” which are replaced by an
exit dialog box – see below) and for new commands introduced in A2 (i.e., change strategies,
sound, about, and help). You are to attach the objects as commands to various combinations
of invokers as shown in the following table (a ‘+’ in a column indicates that the command in
that row is to be able to be invoked by the mechanism in the column header):
Command KeyBinding
Side Menu (or Title Bar
Area) Item Button
accelerate + + +
brake + +
left turn + +
right turn + +
collide with NPR +
collide with base +
collide with energy station + +
collide with drone (g) + +
tick + +
exit +
change strategies +
turn the sound on or off +
give about information +
give help information +
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For west, east, and south regions on the form (Game), you should have a different
Container (another build-in CN1 class) object created. For north and center regions, you
should have a ScoreView and a MapView object created, respectively. ScoreView and
MapView classes should extend from Container. MapView will be an empty container
whereas you should add appropriate labels (use CN1 build-in Label class) to ScoreView
(see below for details). Adding the labels to the ScoreView should be done in the constructor
of the ScoreView. For regions with buttons (i.e., west, east, and south), after you create their
Container objects (which we will call as “control containers”), you should add related buttons
to these containers.
Each button is to have an appropriate command object attached to it, so that when a
button gets pushed it invokes the actionPerformed() method in the corresponding
command object (the execute() method in terms of the Command pattern), which contains
the code to perform the command.
Most commands execute exactly the same code as was implemented in A1. One
exception is the “collide with base” command. Previously this command consisted of a
number (between 1-9) entered from the text field located on the form which we eliminate in A2.
Now, this command is to use the static method Dialog.show() to display a dialog box that
allows the user to enter the number on a text field located on the dialog box (please see the
“Titled Form in CN1” slide of “GUI Basics” chapter in lecture notes for more information). Note
that if the user inputs an invalid value; your program should handle this gracefully.
The other command which must operate slightly different in this assignment is ‘c’
(player’s robot collided with NPR). In A1, this command just increased the damage level of
the player’s robot. Now, the command is to also add damage to one of the NPRs: the ‘c’
command code should choose one NPR and increase that NPR’s damage as well. To make
the game more fair you should really alternate between NPRs when this command is entered,
but it is acceptable to use any algorithm (including choosing an NPR randomly, or always
choosing the same NPR). We will change how this works in the next assignment, so any
approach in A2 is fine.
The “key binding” input mechanism will use the CN1 key binding concept so that the “a”,
“b”, “l”, “r”, “e”, “g”, and “t” keys invoke command objects corresponding to the code previously
executed when the “a”, “b”, “l”, “r”, “e”, “g”, and “t” single-character commands were entered,
respectively. Note that using key bindings means that whenever a key is pressed, the program
will immediately invoke the corresponding action (without the user pressing the Enter key). If
you want, you may also use key bindings to map any of the other command keys from A1, but
only the ones listed here are required.
The “side menu item” input mechanism will use a side menu (see class notes for tips on
how to create a side menu using CN1 build-in Toolbar class). Your GUI will contain a side
menu that contains the following items: “Accelerate”, “Sound”, “About”, and “Exit”. “Accelerate”
menu item should invoke “a” command. “Sound” menu item should include a check box
showing the current state of the “sound” attribute (in addition to the attribute’s state being
shown on the ScoreView container as described below). Selecting the Sound menu item
check box (use CN1 build-in CheckBox class) should set a boolean “sound” attribute to “ON”
or “OFF”, accordingly. The “About” menu item is to display a dialog box (use CN1 build-in
Dialog class) giving your name, the course name, and any other information (for example,
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the version number of the program) you want to display. “Exit” side menu item should invoke
“x” command. Note that in A2 the “x” command should prompt graphically for confirmation and
then exit the program; you should also use a dialog box for this.
Side menu will be placed on the left side of the title bar area. You are also required to
add a “Help” item to the right side of the title bar area. When “Help” is invoked, you are
required to display a dialog box listing the keys user can use while playing the game.
Selecting a side menu item that performs a game command (e.g., “Accelerate” menu
item) should invoke the same code, when the button of the same name had been pushed
(e.g., “Accelerate” button) and/or its related key has been hit (e.g., “a” key). Recall that there is
a requirement that commands be implemented using the Command design pattern. This
means that there must be only one of each type of command object, which in turn means that
the menu items, key bindings, and buttons must share their command objects. (We could
enforce the rule using the Singleton design pattern, but that is not a requirement in A2; just
don’t create more than one of any given type of command object).
The ScoreView class should display game/player-robot state data (i.e., clock value, lives
left, the player robot’s last base reached, the player robot’s energy level, and the player robot’s
damage level), plus one new attribute: “Sound” with value either ON or OFF.1 You should add
several labels to the ScoreView to create this display. As described above, ScoreView must
be registered as an observer of GameWorld. Whenever any change occurs in the world,
GameWorld calls notifyObsersevers() (do not forget to call setChanged() first) which
in turn calls the update() method in its observers (you do not need to call
update()yourself, it is automatically called). In the case of the ScoreView, what update()
does is updating the contents of the labels displaying the game/player-robot state (use Label
method setText() to update the label; if you cannot see a change on labels when you call
setText(), try calling repaint() on the ScoreView). Note that these are exactly the
same game/player-robot state values as were displayed previously (with the addition of the
“Sound” attribute); the only difference now is that they are displayed graphically in
ScoreView.
Although we cover most of the GUI building details in the lecture notes, there will most
likely be some details that you will need to look up using the CN1 documentation (i.e., CN1
JavaDocs and developer guide). It will become increasingly important that you familiarize
yourself with and utilize these resources.
Command Design Pattern
The approach you must use for implementing command classes is to have each
command extend the CN1 build-in Command class (which implements the ActionListener
interface), as shown in the course notes. Code to perform the command operation then goes
in the command’s actionPerformed() method. Hence, actionPerformed() method of
each command class that performs an operation invoked by a single-character command in
A1, should call the appropriate method in the GameWorld that you have implemented in A1
when related single-character command is entered from the text field (e.g., accelerate
command’s actionPerformed() would call accelerate() method in GameWorld).
Hence, most command objects need to have the GameWorld as its target since they need to
1 In this version of the game there will not actually be any sound; just the state value ON or OFF (a boolean
attribute that is true or false). We’ll see how to actually add sound later.
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access the methods defined in this class. You could implement the specification of a
command’s target either by passing the target (reference to GameWorld) to the command
constructor, or by including a “setTarget()” method in the command.
Button class is automatically able to be a “holder” for command objects; Button have a
setCommand() method which allows inserting a command object into the button. Command
automatically becomes a listener when added to a Button via setCommand() (you do not
need to also call addActionListener()), and the specified Command is automatically
invoked when the button is pressed, so if you use the CN1 facilities correctly then this
particular observer/observable relationship is taken care of automatically.
The Game constructor should create a single instance of each command object (for
example, a “Accelerate” command object, a “Brake” command object, etc.), then insert the
command objects into the command holders (buttons, side menu items, title bar area items)
using methods like setCommand() (for buttons), addCommandToSideMenu() (for side
menu items), and addCommandToRightBar() (for title bar area items). You should also
bind these command objects to the keys using addKeyListener() method of Form. You
must call super(“command_name”) in the constructors of command objects by providing
appropriate command names. These command names will be used to override the labels of
buttons and/or to provide the labels of side menu items or title bar area item(s).
Note that commands can be invoked using multiple mechanisms (e.g., from a keystroke
and from a button); it is a requirement that only one command object be implemented for each
command and that the same command object be invoked from each different command
holder. As a result, it is important to make sure that nothing in any command object contains
knowledge of how (e.g., through which mechanism) the command was invoked.
Iterator Design Pattern
The game object collection must be accessed through an appropriate implementation of
the Iterator design pattern. That is, any routine that needs to process the objects in the
collection must not access the collection directly, but must instead acquire an iterator on the
collection and use that iterator to access the objects. You should develop your own interfaces
to implement this design pattern, instead of using the related build-in CN1 interfaces. The
game object collection will implement an interface called ICollection which defines at least
two methods: for adding an object to the collection (i.e., add()) and for obtaining an iterator
over the collection (i.e., getIterator()). The iterator should exist as a private inner class
inside game object collection class and should implement an interface called IIterator
which defines at least two methods: for checking whether there are more elements to be
processed in the collection (i.e., hasNext()) and returning the next element to be processed
from the collection (i.e., getNext()).
Note however the following implementation requirement: the game object collection must
provide an iterator completely implemented by you. Even if the data structure you use has an
iterator provided by CN1, you must implement an iterator yourself: The iterator should keep
track of the current index and it cannot make use of the built-in iterator defined for the data
structure (e.g., you cannot call hasNext() method of the built-in iterator defined for
Vector/ArrayList from the hasNext() method of your iterator class). However, the
iterator can use following build-in methods of the data structure: size() and
elementAt()/get().
Strategy Design Pattern
NPRs move around the world according to their current strategy. That is, the NPR uses
the current strategy of that robot to determine the steering direction and speed, and the
strategy can be changed on the fly (i.e. while the program is running). You are to implement at
least two different NPR movement strategies: the first strategy causes the NPR to move
directly toward the next base (that is, the base with a sequence number one higher than the
one it most recently encountered); the second strategy causes the NPR to update its heading
every time it is told to move so that the heading points toward the location of the player’s robot
(in other words, its strategy is to play “Attack” by trying to collide into the player’s robot). You
may also implement additional strategies if you like, although this is not required (for example,
you might have a strategy where an NPR simply moves in circles, or a strategy where it moves
back-and-forth between two bases).
The program must use the Strategy design pattern to define the strategy for each NPR.
You must use IStrategy interface instead of utilizing an abstract strategy super class. You
should add two methods called setStrategy() and invokeStrategy() and a field for
saving the current strategy to the NPR class. When an NPR is created it should be assigned a
strategy chosen from among the available strategies. It is a requirement that NPRs may not
all have the same initial strategy; other than that you may assign initial strategies however you
choose. Like all game objects, NPRs should include a toString() method; the NPR
toString() should return a string which includes the NPR’s information provided for a player
robot plus an identification of that NPR’s current strategy.
When the human player invokes the “switch strategy” command (which happens when
the appropriate GUI button is pressed), the game should cause all NPRs to switch to a
different movement strategy. Switching strategies is to be done by invoking the NPR’s
setStrategy() method. You may choose the algorithm which determines the new NPR
strategy, as long as every NPR acquires a new strategy each time the “switch strategy”
command is invoked. Additionally, you should arrange that as a side effect of “switching
strategies”, each NPR gets the next “last base reached” value (otherwise, NPRs will never
move beyond Base #2 since we have no command analogous to “collide with base” which
applies to NPRs). Also, you should arrange so that NPRs never run out of energy (e.g., NPRs
do not need to collide with energy, if the NPR’s energy level is getting low, you should set it to
a reasonable value).
Additional Notes
• It is a requirement that the program contain only a single instance of player robot. This
requirement must be enforced via the Singleton design pattern.
• You must use BorderLayout as the layout manager of your form and use FlowLayout
or BoxLayout for the containers you have added to different areas of your form. These
layout managers automatically place and size the containers/components that you have
added to your form/containers.
• You can change the size of your buttons/labels using setPadding() method of Style
class. Each label in ScoreView should be divided into two parts, text and value, and
padding should be added to the value part so that the labels look stable when value
changes as discussed in the class notes. You can also use setPadding() on left and
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right control containers to start adding buttons at positions which are certain pixels below
their upper borders.
• In A2, you must assign the size of your game world by querying the size of your MapView
container (instead of assigning your width and height to 1024×768 as in A1, assign them to
width and height of MapView) using getWidth() and getHeight() method of
Component as discussed in the class notes.
• You must change the style of your buttons using methods like setBgTransparency(),
setBgColor(), setFgColor() of Sytle class so that they look different from labels
as discussed in the class notes. You can extend from the built-in Button class and do the
styling in this new class. Then, while you construct your GUI, instead of creating instances
of the build-in Button class, you can create objects out of this new user-defined button
class.
• Note that all game data manipulation by a command is accomplished by the command
object invoking appropriate methods in the GameWorld (the model). Note also that every
change to the GameWorld will invoke both the MapView and ScoreView observers – and
hence generate the output formerly associated with the “m” and “d” commands. This
means you do not need the “d” or “m” commands; the output formerly produced by those
commands is now generated by the observer/observable process. Please note that even
though some changes to the GameWorld may not relate to the data displayed in all
observers (e.g., changes introduced by the ‘accelerate’ command only relate to the data
displayed in MapView not in ScoreView), every time a change happens, it is okay to
invoke all observers.
• Since almost all commands change the GameWorld (i.e., all command but exit, about,
and help), they produce updated views as side effects. For instance, since the ‘tick’
command causes opponents to move, every ‘tick’ will result in a new map view being
output (because each tick changes the model). Note however that it is not the responsibility
of the ‘tick’ command code to produce this output; it is a side effect of the
observable/observer pattern. You should verify that your program correctly produces
updated views automatically whenever it should.
• You may found the following formula useful while implementing the NPR strategies:
(image from a tutorial at http://www.invasivecode.com/)
Here, (x0,y0) is the current location of the NPR, (x1,y1) is where it wants to go (target),
then B is the ideal compass angle (90 – ideal_heading) for the NPR so it can go towards its
target. Based on this information NPR should change its steering direction accordingly in
order to approach this ideal heading. To calculate arc tan you can use atan() method of
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CN1 MathUtil class which generates angle in “radians”. If you need, you can use
MathUtil.toDegrees() to convert radians to degrees.
• You may not use a CN1’s “GUI Builder” tool for this assignment.
• Programs must contain appropriate documentation as described in A1 and in class.
• Your program must be contained in a CN1 project called A2Prj. You must create your
project following the instructions given at “2 – Introduction to Mobile App Development and
CN1” lecture notes posted at SacCT (Steps for Eclipse: 1) File → New → Project →
Codename One Project. 2) Give a project name “A2Prj” and uncheck “Java 8 project” 3) Hit
“Next”. 4) Give a main class name “Starter”, package name “com.mycompany.a2”, and
select a “native” theme, and “Hello World(Bare Bones)” template (for manual GUI building).
5) Hit “Finish”.). Further, you must verify that your program works properly from the
command prompt before submitting it to SacCT (Get into the A2Prj directory and type
“java -cp dist\A2Prj.jar;JavaSE.jar com.codename1.impl.javase.Simulator
com.mycompany.a2.Starter” for Windows machines. For the command line arguments of
Mac OS/Linux machines please refer to the class notes.). Substantial penalties will be
applied to submissions which do not work properly from the command prompt.
• All functionality from the previous assignment must be retained unless it is explicitly
changed or deleted by the requirements for this assignment.
• As before, you should develop a UML diagram showing the relationships between your
classes/interfaces (and built-in classes/interfaces that your entities extend/implement). This
will be particularly useful in helping you understand what modifications you need to make
to your code from A1.
• You must use a tool to draw your UML (e.g., Violet or any other UML drawing tool) and
output your UML as a pdf file (e.g., print your UML to a pdf file). For your entities you must
use three-box notation (for built-in entities use single-box notation) and show all the
important fields and methods. You must indicate the visibility modifiers of your fields and
methods, but you are not required to show parameters in methods and return types of the
methods.
• Although the MapView container is empty for this assignment, you should put a red border
around it and install it in the form, to at least make sure that it is there (use setBorder()
method of Style class as described in the class notes).
Sample GUI
The following shows how your game GUI should look like. Notice that it has three control
containers containing all the required buttons (on the left, right, and bottom), a side menu and
“Help” item on title bar area, a ScoreView container near the top showing the current
game/player-robot state information, and an (empty) bordered MapView container in the
middle for future use (notice that there is a red border around the MapView). The title “RoboTrack Game” also displays on title bar area.
Deliverables
Submitting your program requires the similar steps as for A1:
1. Be sure to verify that your program works from the command prompt as explained above.
2. Create a “ZIP” file containing (1) your UML diagram in .PDF format, (2) the entire “src”
directory under your CN1 project directory (called A2Prj) which includes source code (“.java”)
for all the classes in your program, and (3) the A2Prj.jar (located under the “A2Prj/dist”
directory) which is automatically generated by CN1 and includes the compiled (“.class”) files
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for your program in a zipped format. Be sure to name your ZIP file as YourLastNameYourFirstName-a2.zip.
3. Create a “TEXT” (i.e., not a pdf, doc etc.) file called “readme.txt” that includes your name
and whether you have tested your submission on a lab machine. You are strongly
encouraged to run and test your program on a lab machine (Hydra terminal server is
recommended) before submitting your project. If you have done this test, also specify the lab
number and the name of the specific machine you have used in that lab (or if you have used
Hyrda as recommended, just say it was tested on Hydra) in the text file. In addition, if you have
done this test, be sure that you include the src folder and jar file generated/tested on the lab
machine in the above-mentioned zip file. This information helps the grader in case your
submission does not work on the machine (s)he uses. You may also include additional
information you want to share with the grader in this text file. You will receive the grader
comments on your text file when grades are posted.
4. Login to Canvas, select “Assignment#2”, and upload your ZIP file and TEXT file separately
(do NOT place this TEXT file inside the ZIP file). Also, be sure to take note of the requirement
stated in the course syllabus for keeping a backup copy of all submitted work (save a copy of
your ZIP and TEXT files).
All submitted work must be strictly your own!
CN1 Notes
Below is the organization for your MVC code for A2. Note that in this organization, we are
using the CN1 “Observable” class and CN1 “Observer” interface to create your GameWorld
and views. Doing it this way has the benefit of CN1 handling the “list of observers” for you.
Note also that this pseudo-code shows one way of registering Observers with Observables:
having the controller handle the registration. It is also possible to have each Observer handle
its own registration in its constructor (examples are shown in the course notes). You may use
either approach in your program.
public class Game extends Form {
private GameWorld gw;
private MapView mv; // new in A2
private ScoreView sv; // new in A2
public Game(){
gw = new GameWorld(); // create “Observable” GameWorld
mv = new MapView(); // create an “Observer” for the map
sv = new ScoreView(); // create an “Observer” for the game/player-robot
// state data
gw.addObserver(mv); // register the map observer
gw.addObserver(sv); // register the score observer
// code here to create Command objects for each command,
// add commands to side menu and title bar area, bind commands to keys, create
// control containers for the buttons, add buttons to the control containers,
// add commands to the buttons, and add control containers, MapView, and
// ScoreView to the form
this.show();
… // code here to query MapView’s width and height and set them as world’s
// width and height
gw.init(); // initialize world
}
}
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public class GameWorld extends Observable {
public void init(){
//code here to create the initial game objects
}
// additional methods here to manipulate game objects and related game state data
}
public class MapView extends Container implements Observer {
public void update (Observable o, Object arg) {
// code here to call the method in GameWorld (Observable) that output the
// game object information to the console
}
}
public class ScoreView extends Container implements Observer {
public void update (Observable o, Object arg) {
// code here to update labels from the game/player-robot state data
}
}