Lab 9

Overview

For this lab, you will revise your Lab 8 solution by introducing arrays of ParkingLots in the District class.

Resources

You will need to use the ParkingLotsDriver.java to test your implementation of modified ParkingLot and District classes.

Assignment

The previous version of the District class you delivered was limited to districts with three parking lots. This was an artificial limit, and you have been contracted to revise the code to support up to twenty parking lots per district. You are to replace the lot1, lot2, and lot3 instance variables in District by an array, lots, of ParkingLot items. The array is to support up to 20 parking lots. You will introduce a variable numLots to track the number of parking lots currently in use. In addition, you will make a small modification to ParkingLot as described below.

You should create a lab 9 project using the GitHub classroom invitation for lab 9. This project will contain a new driver class, ParkingLotsDriver.java. You'll need to copy your ParkingLot and District classes from your lab 8 project. Begin by fixing any known issues with your lab 8 submission.

The following diagram shows the revised API that you are to implement. Detail on each change is given below.

ParkingLot

+CLOSED_THRESHOLD: double {readOnly} = 80.0
-name: String {readOnly}

+ParkingLot(name: String, capacity: int)
+ParkingLot(capacity: int)
+getMinutesClosed(): int
+getName(): String
+getNumberOfSpotsRemaining(): int
+getPercentFull(): double
+isClosed(): boolean
+markVehicleEntry(timestamp: int): void
+markVehicleExit(timestamp: int): void
+toString(): String

District

-lots: ParkingLot[]
+MAX_LOTS: int {readOnly} =20
-numLots: int

+District()
+addLot(name: String, capacity: int): int
+getLot(index: int): ParkingLot
+getMinutesClosed(): int
+getNumberOfSpotsRemaining(): int
+isClosed(): boolean
+markVehicleEntry(lotNumber: int, timestamp: int): void
+markVehicleExit(lotNumber: int, timestamp: int): void
+toString(): String

Changes to `ParkingLot`

You will need to make the following changes to your ParkingLot class:

Update the class based on lab 8 feedback from your instructor (if available)
Replace the displayStatus() method with a toString() method. This method is to return a string of the form "Status for [name] parking lot: [x] vehicles ([p])" where [name] is replaced with the name of the lot, [x] is replaced with the number of vehicles currently in the lot, and [p] is replaced with the percentage of the lot that is occupied. As before, the percentage occupied is formatted with at most one digit after the decimal and "CLOSED" if the percentage is at or above CLOSED_THRESHOLD. The DecimalFormat class using a pattern of #.# can be used to format the numerical percentage. (See this Taylorial page for some examples of how to use the DecimalFormat class.)

Having toString() is good practice because it allows the client code to print other places besides System.out.

Changes to `District`

Most of the changes are to District, but you might notice that the parameters and return types for existing methods do not change. Specifically:

Update all District documentation to match the new behavior.
Replace the old District constructor with the no-argument constructor below.

    public District() {
        lots = new ParkingLot[MAX_LOTS];
    }

Declare a class constant called MAX_LOTS. Set it to 20.
Replace the declaration for lot1, lot2, and lot3 with an array of ParkingLots called lots
Add an instance variable numLots to track the number of lots actually in use.
Add a method addLot() (see the class diagram) with the following code:

        int newIndex = numLots;
        if(newIndex<MAX_LOTS) {
            lots[newIndex] = new ParkingLot(name, capacity);
            numLots++;
        }
        // return the index of the new lot or -1 if the lot was not added.
        return newIndex<MAX_LOTS ? newIndex : -1;

Add a method getLot which returns the ParkingLot at the given index. Note that lot numbers now start at 0. A precondition for this method is that the lot index is valid.
Rewrite markVehicleEntry, markVehicleExit, getNumberOfSpotsRemaining, and isClosed so they use getLot to retrieve the approriate parking lot.
Rewrite displayStatus() as toString(). The value returned by toString() will be a string with newline characters embedded in it. For example, toString() could return a string such as:

District status:
  Status for purple parking lot: 8 vehicles (CLOSED)
  Status for gold parking lot: 20 vehicles (33.3%)

Here you should call ParkingLot.toString() for each line, prepending two spaces and appending "\n" for the newline. There should be a newline at the end of each line including the last.

Testing and Sample Output

The ParkingLotsDriver exercises most of your code. The output is given below, but remember that having slightly different numbers may be okay and that matching this output does not automatically mean your solution is correct.

Testing Small Lot...
Status for Blacktop parking lot: 0 vehicles (0%)
Finished Testing Small Lot

Testing Overfilling a Lot...
Finished Testing Overfilling a Lot

More Complete Test of Parking Lot...
Testing ParkingLot
Status for test parking lot: 3 vehicles (75%)
Status for test parking lot: 4 vehicles (CLOSED)
Status for test parking lot: 2 vehicles (50%)
Status for test parking lot: 0 vehicles (0%)
Final status: Status for test parking lot: 0 vehicles (0%)
Finished More Complete Test of Parking Lot

Testing Coming and Going...
Finished Testing Coming and Going

Testing Tiny District...
Tiny District status:
  Status for Red parking lot: 0 vehicles (0%)
  Status for Green parking lot: 0 vehicles (0%)
  Status for Blue parking lot: 0 vehicles (0%)

District status:
  Status for Red parking lot: 1 vehicles (CLOSED)
  Status for Green parking lot: 0 vehicles (0%)
  Status for Blue parking lot: 2 vehicles (CLOSED)

Final Tiny District status:
  Status for Red parking lot: 0 vehicles (0%)
  Status for Green parking lot: 1 vehicles (CLOSED)
  Status for Blue parking lot: 2 vehicles (CLOSED)

Lots were closed for 3 min. in tiny district.
Finished Testing Tiny District

Finished Testing Normal District...
Airport at timestamp 7:
District status:
  Status for Brown parking lot: 7 vehicles (70%)
  Status for Green parking lot: 14 vehicles (CLOSED)
  Status for Black parking lot: 7 vehicles (58.3%)

Airport at timestamp 8:
District status:
  Status for Brown parking lot: 8 vehicles (CLOSED)
  Status for Green parking lot: 14 vehicles (CLOSED)
  Status for Black parking lot: 7 vehicles (58.3%)

Airport at timestamp 10:
District status:
  Status for Brown parking lot: 8 vehicles (CLOSED)
  Status for Green parking lot: 14 vehicles (CLOSED)
  Status for Black parking lot: 10 vehicles (CLOSED)

Finished Testing Normal District

Finished Testing Heavily Used District...
At end of day, all lots closed 42 min.
Final District status:
  Status for Pink parking lot: 17 vehicles (68%)
  Status for Blue parking lot: 28 vehicles (CLOSED)
  Status for Gray parking lot: 2 vehicles (20%)

Finished Testing Heavily Used District

All tests finished.

Acknowledgement

This laboratory assignment was developed by Dr. Rob Hasker and the CS1011 instructors.

See your professor's instructions for details on submission guidelines and due dates.