CS 109/113 - Computer Science 1

Writing classes

In this lab you will:

Use the Scanner class to read from a file via System.in
Write a class
Write several methods for that class

This lab is critical for this week's homework so be sure you finish it during your lab session, and ask for help if you need it!

For this and other Lab Activities, you are encouraged to collaborate with your classmates, especially when it comes to addressing any issues that come up, error messages that you receive, etc. Because this lab is critical for the homework, be sure you save a complete copy of the work you did.

Tracking Airline Flights

Keeping track of airplane flights is hard. There are a lot of flights, and there is a lot of information about each flight. In this lab you will work with real data concerning flights into or out of Philadelphia airport in 2008. There were almost 200,000 of them.

To handle all of that information through this lab and this week's homework you will develop a class to hold information about a single flight. Then you will put all of that information into an array.

For this lab you will work with a very small subset, 3 flights, of the actual data.

Part 1 -- Define a Flight class

Part 1: Define a Flight class First you will create a class that represents a single flight from one airport to another. This class will be used in the second part of this Lab and throughout this week's homework. Each flight contains information about:

The year, month, and day of the flight
The flight number
The departure delay and arrival delay
The origin airport and destination airport

In this part of the assignment, implement a Flight class consisting of the following instance variables and methods:

Instance Variables
- year -- integer
- month -- integer
- day -- integer
- flight number -- integer
- departure delay -- integer
- arrival delay -- integer
- origin airport -- String
- destination airport -- String
public methods
- Constructor
  - Flight(int y, int m, int d, int fn, int dd, int ad, String orig, String dest)
- Accessor methods
  - int getFlightNumber()
  - int getDepartureDelay()
  - int getArrivalDelay()
  - String getOrigin()
  - String getDestination()
- Printing Methods
  - String getDate()
    return a string of the form "mm/yy/yyyy"
  - String toString()
    return a string of the form "mm/dd/yyyy FN:ffff Origin:oooo Destn:dddd departure delay:yyyy minutes arrival delay:aaaa minutes"
    in the above string mm,dd,yyyy,oooo,dddd,yyyy,aaaa are all to be replaced by the values stored in the instance

Two thoughts / requirements:

All of the instance variables must be private
The toString method must use the getDate method.

Once you have implemented the Flight class as described above, write a main() method for the Flight class that tests the Flight class by creating a new instance and then printing the object, for example:

   public static void main(String[] args) {
       Flight f = new Flight(2020, 11, 23, 113, 3, 8, "PHL", "SFO");
       System.out.println(f);
   }

Compile and run your program. Make sure that the output looks exactly like what you want.

Part 2: Create a flight data reader

Next, you will create another class, FlightReader, that enables other programs to read flight data about several flights. For example, here are the contents of a small data file, which I refer to as testFlights.txt: 3 2020 11 23 113 3 8 PHL SFO 2020 11 24 206 2 -3 ORD PHL 2020 11 25 231 0 4 PHL SEA You can create a file containing this data for yourself or copy it from

    /home/gtowell/Public/CS113/LAB7/testFlights.txt

using the standard cp or scp commands.

The file contains information for three flights. The first line indicates how many flights are recorded in the file. The remaining lines contain the data. Each line contains the following data, separated by a space, in exactly this order:

year
month
day
flight number
departure delay
arrival delay
origin airport
destination airport

Create a class called AllFlights that contains a static method called readFlights() that takes no input parameters. This method should work as follows:

Create an instance of the Scanner class that reads the file. Note that you will need to wrap the method in a try..catch as opening a file for reading can throw an exception that Java required you to catch. To jog your memory, the method should contain code like the following:
```
            try {
                Scanner scnr = new Scanner(new File(filename));
            } catch (Exception except) {
                System.out.println("Problem: " + except);
            }
        
```
Read the first number from the file. I call tht number "N", below.
Loop N times, each time reading a complete line of data from the file. (Do this by calling the scanner instance to read the 8 items on a line.)
Store each of the 8 items into 8 separate variables.
As needed, convert each item to the appropriate time -- Alternately, note that Scanner has a methods nextInt() that will do some of the conversions for you.
Print the data about a flight. Ideally do this by putting the 8 data items into a Flight object, and then use the toString method you wrote in part 1.

When creating Flight objects, the readFlights() method should read the data of the appropriate type using the Scanner instance opened in the first step.

Compile and run your program. Make sure that the output is as you expect.

What to hand in

Use your phone to take a picture of a terminal window showing the program you ran in the last step above (ie showing the formatted output for the testFlights.txt file). Send the picture to gtowell@brynmawr.edu