Purpose
A multi-dimensional array is an important data structure that is
suitable for many programming situations. In this assignment, you will
gain experience designing and implementing a 2-dimensional array. These
experiences can be readily generalized to arrays with more than only 2
dimensions. This new programming capability can be valuable
as you design and develop programs in the future.
The second purpose of this assignment is to complete the Trader
game design and implementation. Only one more class needs to be
designed and implemented: the Universe class.
This assignment creates a new flexibility because of the Descriptions
class and the Map class, which you designed and implemented in the last
few labs. The Descriptions class provides the capability to randomly
choose such properties as the Location names, the adjective describing
each Location, and the Cargo names and cost factors. The important
capability that the Map provides is to print out the Universe, noting
where the user currently is. We will exploit each of these as we create
the Universe class to complete our game.
Files
| To get started, create a new directory called
HWJ8, and download
Universe.java,
Market.class,
Location.class,
Inventory.class,
Map.class,
Vehicle.class,
Cargo.class,
Parser.class, and
Game.java (right click on each link, select "save as", and
save them all to this directory). Note that in this assignment
the only file you should modify is Universe.java. As with the
previous assignments,
you are free (and even encouraged) to use your versions of the
previous Java classes (e.g., Market, Location, Inventory,
Map, Vehicle, Cargo, Parser) using the technique described in the
last homework assignment. Make sure
that when you're done either
downloading or copying your own
versions to this directory, you have all 9 of the above Java classes (either source code or bytecode) in this directory. You should use your own Descriptions.java file, as that will allow
your Universe to have the names you came up with in lab 10.
If you do not have it (or it doesn't work), you can download ours
here. Remember, if you use your
Descriptions.java file, then the CORRECT implementation of
'getCargoCostFactor' must use '.equals' instead of
'==' for the string comparison.
Note that the Java documentation for all of the
existing classes can be found
here. There is a remaining HW J7 issue that a lot
of people ran into, and will manifest itself in this assignment
as well. If you are using our Location.class file above,
then you can skip this paragraph; if you are using yours,
definitely read this paragraph. In HW J7, our intent with
the Inventory class was to create a Cargo array of
Game.MAX_INVENTORY_SIZE (currently set to 15), but only put
Game.DEFAULT_INVENTORY_SIZE (currently 5) Cargo objects in the
inventory. If you use the same value for the array size
and the number of Cargo elements in it, then you can never sell
an item in a Market (as their inventory is always full).
This wasn't explained very well in HW J7.... |
Universe class
The Universe is used to represent the Locations that the Vehicle
can travel to in order to buy and sell goods. Note that we could
(and have) encoded these locations as a list (Vector), but a
2-dimensional array is a better representation, in part because a
2-dimensional array is intuitively a better fit.
You might be asking yourself, "Didn't we define a 2-D array as part
of Lab 11 on the Map class? Why are we doing it again?" This is
not the case. In Lab 11, we assumed that a particular 2-D array
already existed, and we performed operations on it. That is, in
Lab 11, we did not define the array itself, but used the methods from
the Universe class instead. This is the assignment where we
actually define the array in this Universe class. Attributes
- universe (Location[][]): The data structure
that contains the Locations of the Universe, indexed by
(row,col) coordinates
- density (double): Roughly, this is the
probability that a Location exists at a particular X-Y
coordinate of the Universe. Note that the semantics of
this field is that if a given Universe has a density of
"0.1", then it is NOT necessary that precisely 10% of
the coordinates contain an actual instance of a
Location. This is like saying that if I flip a
coin 100,000 times, then "heads" will come up
approximately 50,000 times. But if I flip a coin only 4
times, then it's possible that "heads" would happen
twice, although I shouldn't be surprised if I get three
"heads".
Accessors/Mutators
Of course, these instance variables in this class should
be declared private and manipulated via accessor and mutator
methods as we have discussed during lecture. Thus, you must
include an accessor and mutator method for each of
the above fields in both classes. The name of the accessor/mutator
should follow the standard Java naming conventions (i.e.
getPosX(), setName(),
etc.). All the mutators must check for invalid
values being passed in -- what you do when you find an
invalid value is your choice (print an error message, not
change the value, etc.).
Other methods
The location class should also support the
following methods:
- Universe ():
The default constructor, it initializes the Universe to
default values. The default for the height, width,
and density are constants in the Game class (UNIVERSE_HEIGHT,
UNIVERSE_WIDTH, and UNIVERSE_DENSITY). Note that
the constructors do NOT put Location objects in the
Universe -- this is done via the populate() method.
- Universe (int theHeight, int theWidth, double theDensity):
The specific constructor initializes the density to
the passed value. This method also initializes the
universe array to the passed dimensions. Note that
since the array is indexed by (row,col) coordinates,
then this method should create the array of size (theHeight,
theWidth). Note that the constructors do NOT put
Location objects in the Universe -- this is done via the
populate() method. Note that Game.java calls the
specific constructor, and creates a universe that is 10
columns wide by 12 rows high -- if yours is 12x10, then
something is wrong.
- int getNumCols(): this method returns the
number of columns (i.e. the width) of the Universe.
It should determine this by the dimensions of the 2-D
universe array. If you forget how to do this, see
slide 80 in the
lecture notes on arrays.
- int getNumRows(): this method returns the
number of rows (i.e. the height) of the Universe.
It should determine this by the dimensions of the 2-D
universe array. If you forget how to do this, see
slide 80 in the
lecture notes on arrays.
- void populate(): This method will fill the
universe array with locations. For each spot in the 2-D array, the
chance of having a Location at that spot is density.
So if density is 0.1, then there is a 10% change that
each spot has a location. You can obtain a random
number via Game.rand.nextDouble(). Thus, for each
spot in the 2-D array, obtain a random number via
Game.rand.nextDouble(). If that random number is
less than density, then that spot should hold a new
Location; otherwise, it should hold null.
Note that if your
universe is too large (for example, if you change the
size of the the universe's height and width in Game.java), and thus the populate()
method tries to create more Locations than
there are names in Descriptions.getLocation(),
then your Game.java will hang in an infinite loop -- so
don't create too large
a universe (you can
experimentally
determine roughly the
threshold for "too large"). If a Location
is to be at a given spot, the following are the values
for that Location (in
other words, the
parameters to the
invocation of the constructor):
- The name is from Descriptions.getLocationName(),
but must be unique -- meaning one that does not exist
already. So you need to check if the name exists
already (if so, get a new one). You should use the
findLocationByName() method for this. The
createUniqueInventory() method in the Market class does
something similar (in that case, it creates unique cargo
names).
- The appearance is
determined by
Descriptions.getAppearance().
It's okay if multiple Locations in the universe have
the same appearance.
- The row and col coordinates are for the particular
position in the 2-D array.
- The location's market should be created with a
random cost factor that is between 0.0 and
Game.MAX_COST_FACTOR (obviously, the cost
factor can't be 0.0 itself).
- void setLocationAt (int row, int col, Location
loc): This method sets the location at (row, col) to
the passed Location value.
- Location getLocationAt (int row, int col): Returns
the Location at the coordinates (row,col). If no such
Location exists, then null is returned.
- Location getRandomLocation(): Chooses and
returns one of Locations in the Universe at random. An easy way to
do this is to add all the locations into a vector,
shuffle the vector (via
Collections.shuffle()), and then return the first
element in that vector.
- Location findLocationByName(String dest):
This method looks through all of the Locations in the Universe until
finding the one with the name "dest". If no such named
Location exists, returns null.
Final Version of the Game
Here is a sample output. The input that the user entered is shown in red.
Note that this output only deals with traveling from one location to
another. The other aspects of the game (buying and selling
goods, etc.) aren't shown below.
Welcome to CS101 Space Trader v4!
Your InterGallactic Thunderbird is starting at Higgin's Moon (8.0,9.0).
You burn fuel at the rate of 5.00 gozorkas per million kilometers.
You are at a Higgin's Moon
You have $1,000.00 on hand
Valid commands are:
travel (to travel to another location)
market (to enter the market)
worldmap (to print out the map)
inventory (to show your inventory)
quit (to leave the game)
You can abbreviate any command by its first letter
Enter next command: t
Printing Universe
1 - - - - - - - - -
2 - - 3 - 4 - - - -
- - - - - - - - - 5
- - - - - - - - - 6
- - - - - 7 - - 8 -
- - - - - 9 - - - 10
- - - - - - - - - -
- 11 - - - 12 - - - -
- - - - - - 13 - - 14
- - - - - - - - - -
- - - - - 15 - - - -
16 - - 17 - - - - - -
The valid destinations are:
1: Newhall
2: Muir
3: Heinlein
4: Ezra
5: Boros
6: Londinium
7: Hera
8: Triumph
9: Sihnon
10: Osiris
11: Santo
12: Athens
13: Beylix
14: Higgin's Moon (your location)
15: Bernadette
16: St. Albans
17: Regina
Enter the name of the destination you want to travel to: Triumph
This is a distance of 4.12 million kilometers
This will require 20.62 gozorkas of fuel
You have 1,000.00 gozorkas of fuel on board
You travel to Triumph
You have 979.38 gozorkas of fuel on board
You are at a Triumph
You have $1,000.00 on hand
Valid commands are:
travel (to travel to another location)
market (to enter the market)
worldmap (to print out the map)
inventory (to show your inventory)
quit (to leave the game)
You can abbreviate any command by its first letter
Enter next command: m
Welcome to the market at Triumph (4.0,8.0). The cost factor here is 0.10
You are at the market. You have $1,000.00 on hand
Valid commands are:
buy (to buy cargo)
sell (to sell cargo)
available (to see what's available to buy)
inventory (to show your inventory)
exit (to exit the market and return to the location)
Enter next command: b
Possible items to trade:
0: 4 units of Aluminum at $0.02 per unit (total price in market: $0.06)
1: 3 units of Gold at $0.90 per unit (total price in market: $2.70)
2: 4 units of Medicine at $2.50 per unit (total price in market: $10.02)
3: 7 units of Java textbooks at $30.91 per unit (total price in market: $216.35)
4: 8 units of Waste at $0.72 per unit (total price in market: $5.75)
Which one do you want to trade? 0
It will cost $0.06 for this purchase
You are at the market. You have $999.94 on hand
Valid commands are:
buy (to buy cargo)
sell (to sell cargo)
available (to see what's available to buy)
inventory (to show your inventory)
exit (to exit the market and return to the location)
Enter next command: b
Possible items to trade:
0: 3 units of Gold at $0.90 per unit (total price in market: $2.70)
1: 4 units of Medicine at $2.50 per unit (total price in market: $10.02)
2: 7 units of Java textbooks at $30.91 per unit (total price in market: $216.35)
3: 8 units of Waste at $0.72 per unit (total price in market: $5.75)
Which one do you want to trade? 0
It will cost $2.70 for this purchase
You are at the market. You have $997.24 on hand
Valid commands are:
buy (to buy cargo)
sell (to sell cargo)
available (to see what's available to buy)
inventory (to show your inventory)
exit (to exit the market and return to the location)
Enter next command: b
Possible items to trade:
0: 4 units of Medicine at $2.50 per unit (total price in market: $10.02)
1: 7 units of Java textbooks at $30.91 per unit (total price in market: $216.35)
2: 8 units of Waste at $0.72 per unit (total price in market: $5.75)
Which one do you want to trade? 0
It will cost $10.02 for this purchase
You are at the market. You have $987.22 on hand
Valid commands are:
buy (to buy cargo)
sell (to sell cargo)
available (to see what's available to buy)
inventory (to show your inventory)
exit (to exit the market and return to the location)
Enter next command: e
You are at a Triumph
You have $987.22 on hand
Valid commands are:
travel (to travel to another location)
market (to enter the market)
worldmap (to print out the map)
inventory (to show your inventory)
quit (to leave the game)
You can abbreviate any command by its first letter
Enter next command: t
Printing Universe
1 - - - - - - - - -
2 - - 3 - 4 - - - -
- - - - - - - - - 5
- - - - - - - - - 6
- - - - - 7 - - 8 -
- - - - - 9 - - - 10
- - - - - - - - - -
- 11 - - - 12 - - - -
- - - - - - 13 - - 14
- - - - - - - - - -
- - - - - 15 - - - -
16 - - 17 - - - - - -
The valid destinations are:
1: Newhall
2: Muir
3: Heinlein
4: Ezra
5: Boros
6: Londinium
7: Hera
8: Triumph (your location)
9: Sihnon
10: Osiris
11: Santo
12: Athens
13: Beylix
14: Higgin's Moon
15: Bernadette
16: St. Albans
17: Regina
Enter the name of the destination you want to travel to: Londinium
This is a distance of 1.41 million kilometers
This will require 7.07 gozorkas of fuel
You have 979.38 gozorkas of fuel on board
You travel to Londinium
You have 972.31 gozorkas of fuel on board
You are at a Londinium
You have $987.22 on hand
Valid commands are:
travel (to travel to another location)
market (to enter the market)
worldmap (to print out the map)
inventory (to show your inventory)
quit (to leave the game)
You can abbreviate any command by its first letter
Enter next command: m
Welcome to the market at Londinium (3.0,9.0). The cost factor here is 1.00
You are at the market. You have $987.22 on hand
Valid commands are:
buy (to buy cargo)
sell (to sell cargo)
available (to see what's available to buy)
inventory (to show your inventory)
exit (to exit the market and return to the location)
Enter next command: s
Possible items to trade:
0: 4 units of Aluminum at $0.16 per unit (total price in market: $0.63)
1: 3 units of Gold at $9.05 per unit (total price in market: $27.15)
2: 4 units of Medicine at $25.23 per unit (total price in market: $100.92)
Which one do you want to trade? 0
You are at the market. You have $987.85 on hand
Valid commands are:
buy (to buy cargo)
sell (to sell cargo)
available (to see what's available to buy)
inventory (to show your inventory)
exit (to exit the market and return to the location)
Enter next command: s
Possible items to trade:
0: 3 units of Gold at $9.05 per unit (total price in market: $27.15)
1: 4 units of Medicine at $25.23 per unit (total price in market: $100.92)
Which one do you want to trade? 0
You are at the market. You have $1,015.00 on hand
Valid commands are:
buy (to buy cargo)
sell (to sell cargo)
available (to see what's available to buy)
inventory (to show your inventory)
exit (to exit the market and return to the location)
Enter next command: s
Possible items to trade:
0: 4 units of Medicine at $25.23 per unit (total price in market: $100.92)
Which one do you want to trade? 0
You are at the market. You have $1,115.93 on hand
Valid commands are:
buy (to buy cargo)
sell (to sell cargo)
available (to see what's available to buy)
inventory (to show your inventory)
exit (to exit the market and return to the location)
Enter next command: e
You are at a Londinium
You have $1,115.93 on hand
Valid commands are:
travel (to travel to another location)
market (to enter the market)
worldmap (to print out the map)
inventory (to show your inventory)
quit (to leave the game)
You can abbreviate any command by its first letter
Enter next command: q
You ended the game with $1,115.93
Goodbye!
Congratulations, Space Trader!
Your InterGallactic Thunderbird traveled 5.54 million kilometers.
You still have 972.31 gozorkas of fuel available.
Take the rest of the day off, Space Trader -- you deserve it!
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