This is an individual lab.
A common travel game is to find the letters in a word on the license plates of vehicles that you see on the road. For example, the license plates ATT-351 and CPO-OO3 would be sufficient to match "CAT". For this lab, you will be given code that draws cars, buses, and a person moving around a map. As the person comes into contact with a car, that car's plate will be used to match letters in various keywords. The first keyword you will match is "MSOE". Your implementation will use the Observer Pattern.
The starting point for this lab is
at se2811-mketour.zip
.
(Note: if your instructor is using Github Classroom, this code may
be in your repository as soon as you create it.)
A key class being given to you is CityMap
. It displays a portion
of Milwaukee. This map is just for reference - your game pieces will not
actually follow the roads and will even float across the harbor. This map
also includes a Museum
represented by a rectangular area you
can walk
through. The moving objects are subclasses of the abstract
class MobileEntity. We use the term "tagging" to mean colliding
with another object. The base class Taggable
are those objects
that can collide with other objects.
The following diagram shows the relationship between the objects on the map:
CityMap
has multiple museums and entities. The entities are in
an actors
package:
src/mketour/img
)
when the user enters the art museum. Display "MSOE CHALLENGE COMPLETED"
when all of the target letters in MSOE are found, and "BUS CHALLENGE
COMPLETED" when all of the letters in BUS are found.
A sample image of
game play in progress is
This shows what it looks like after the player has tagged the art museum,
plates with the letters M and O, and a bus. Note all of these items are
shown in the right hand window. Also note the BUS challenge only
shows after the user tags (hits) a bus. The person is guided on the map by
dragging the green circle (the goal circle). The initial game status would
be shown as
Challenge: Find all the letters in MSOE
Goal: MSOE
Found: ****
Challenge: Find art
A good place to start is by implementing an observer that displays The Wood Gatherer when the person enters the Milwaukee Art Museum box. Then implement the observer for license plates matching the goal "MSOE". Finally, you should be able to implement the observer for matching the goal "BUS" by reusing previous observers.
How you use the Observer Pattern is one of the many
choices you need to make in this assignment. One approach is to take an
existing domain object or objects (such as Person
, Car
,
or MobileEntity
) and make that the subject. Another approach is
to make the event of tagging an object (such as when the bus tags the
person) into a subject. A related question is what data to pass in the
operation to update the observers. You could pass the objects being tagged,
the subject that is producing the event, or data such as license
plates. These choices have no clear answers, and the "best" solution often
comes down to the one that makes the most sense to individual students. Do
not be afraid to experiment! No matter what you do, make
sure how you are using the pattern isolates your observers and
your subjects. There should be very little communication between
your observers and your subjects.
A major part of this assignment is implementing the Observer Pattern. You
are to write your own classes implementing this pattern; do not
use Java.util.Observable
or Java.util.Observer
. You may
use your own names for the Observer Pattern; it may be helpful to use
names that are specific to the problem such as "CarObserver" or "TagObserver."
Solutions should not need to use casting. For example, you should not need
to cast from an Object
to Taggable
.
One goal of the Observer Pattern (like other patterns) is to simplify
future modifications to existing code when supporting new features. You
should not need to modify existing classes other than to introduce the code
for the pattern and to modify CityMap.addEntities()
to support a
new challenge.
When you submit, check that CityMap.DEBUG_LEVEL
is 0 so any
debug code is disabled. Console messages about contacting buses and museums
might be useful to you, but large numbers of messages slow down your
solution and make it difficult to grade. Make sure all of your output is
controlled by DEBUG_LEVEL
.
See your instructor for submission directions.
This lab was developed by Dr. Yoder in Winter 2018-19.