CSE116A,B  Introduction to CS II for Majors : LAB 3


Objectives: 

1. Make a package of classes.
2. Using and REUSING a classes from a package.

Problem Statement: In this lab we will create two useful classes for
banking applications called BankUI and BankAccountRecord in a package
named "bank". We will test this package by using it in an application
that creates ineteractively new accounts and stores them in a
sequential file. Then we will use the same package in another
application CreditInquiry that simply lists all the accounts in
credit, debit and zero balance categories.

TO DO:

1. In your cse116/fall2000/lab directory (you should have one by now)
   create a new directory "bank". This directory will hold the two
   classes that go in the package. 
   mkdir bank
   cp ~bina/cse116/fall2000/lab/bank/*.java .

2. Study the two programs. Open BankUI.java. Add a line 
   
   package bank;

   after the comments at the beginning of the file. Save it.

3. Repeat the same for the other file: BankAccountRecord.java.

4. Compile: javac BankUI.java
            javac BankAccountRecord.java

5. Now change directory to the parent directory.
   cd ..
  
6. Create another directory named lab4. Change directory to lab4.

   mkdir lab4
   cd lab4

7. Copy the first application CreateSequentialFile.java.

   cp ~bina/cse116/fall2000/lab/lab4/CreateSequentialFile.java .

8. Add a line that imports the classes from bank package.
   import bank.*;
  
9. Save it. Compile it.
   
   javac CreateSequentialFile.java

10. Observe the errors. What is happening? Explain. It is not able to
    fine "bank" package? How to solve this problem. One of the
    solutions is to add a classpath to where the pacakge is located.
    Next step shows how to do this.

11. Go to your home directory.
    
    cd
   
12. Edit your .cshrc file to include a CLASSPATH that includes the
    path of the directory where "bank" is located. This will be 
    /u0/faculty/bina/cse116/fall2000/lab/  for me. You can find out
    about the path by typing in "pwd" after moving to the directory
    where "bank" is located.
    Add this to you CLASSPATH environment variable. Your TA may help
    with this. Or you can see my .cshrc file for example.

    After updating your CLASSPATH environment variable, you will
    have to source your .cshrc file.

    source .cshrc

13. Now you get back to your lab4 directory and compile. It should go
    fine. Execute your program using java CreateSequentialFile

14. When it asks for a file name using the "FileChooser" that appears
    on the screen, navigate to your lab4 directory and type in
    lab4Data as the name for the data file.

15. After entering 3 sets of data, one with positive balance, one with
    negative balance and one with 0 balance, close the application.

16. Now copy another application CreditInquiry from
    ~bina/cse116/fall2000/lab/lab4 to your lab4 directory. It uses the 
    same package "bank". Compile it and run it. You will see the data 
    you entered in the first application getting displayed by this 
    application.

17. Close the application.

18. Run CreateSequentialFile application and CreditInquiry one after
    another in the background. You can see the update from one
    application getting displayed in the second application
    concurrently.

    java CreateSequentialFile &
    java CreditInquiry &

19. Close the applications after experimenting with their features.

20. Study the programs and understand the reusability of the classes
    in the pacakge "bank". Observe the this is not a robust program.
    (You may try out your exception handling skills from last lab..
     thouugh it is not a required element of this lab..).