Homework Assignment 4

Adding File Interaction to AssociationLists

810:062
Computer Science II
Object-Oriented Programming

Due: Thursday, February 17, at 8:00 AM

Introduction

This assignment asks you to add to the AssociationList class the ability to remember Associations between executions. We will do that by giving AssociationList methods for loading Associations from a file and saving them to a file.

Tasks

Add these behaviors to the AssociationList class:

1. The user can ask an AssociationList for its size.

2. The user can ask an AssociationList to clear itself, which results in the AssociationList containing no Associations.

3. The user can ask an AssociationList to saveToFile, passing the name of the output file as a String argument. In response, the AssociationList writes all of its Associations to the target file. It does not change its own state.

4. The user can ask an AssociationList to loadFromFile, passing the name of the input file as a String argument. In response, the AssociationList reads all of the Associations in the source file and adds them to its collection. Any Associations that were already in the AssociationList will still be there.

5. The user can ask an AssociationList to loadFromFileSorted, passing the name of the input file as a String argument. In response, the AssociationList reads all of the Associations in the source file and adds them to its collection. It adds the new Associations in ascending order of their keys as it adds to its vector. Any Associations that were already in the AssociationList will still be there, in the order they already were in.

Do the following to demonstrate your code:

1. Write a driver class named AssociationListDemo that
   • creates an AssociationList,
   • adds at least ten Associations in unsorted order to the AssociationList,
   • writes the AssociationList to a file named "notes-unsorted.txt",
   • clears the AssociationList,
   • reads the Associations back into the AssociationList in sorted order, and
   • writes the AssociationList to a new file named "notes-sorted.txt"

Use the code from Session 10 as a starting point for your code that reads and writes files. Don't forget the new import directives that you'll need to add to your class in order to use the new I/O classes.

As always, write your program in the style we have been using all semester. First, write a test that expresses what you would like your code to do. Then write the code to do it. Finally, refactor your code to improve the design. Use the GenerateTest program to create your test class.

Take small steps, and your tests will give you feedback as soon as possible. For each task above, you should be able to write at least two tests. For the tasks that involve files, you should probably write even more.

For example, I would write saveToFile() by first writing a test that writes an empty AssociationList to a file. Why? Because then I can be sure that my code can create a new text file successfully before I have to worry about how to write actual Associations to the file.

For now, you will have to visually inspect the output file generated by saveToFile(), because you don't yet know enough Java to do it in a JUnit test. What do you imagine we will need to do to write a test in Java?

Deliverables

By the due date and time, submit the files

• AssociationListTest.java
• AssociationList.java
• AssociationListDemo.java
• notes-unsorted.txt
• notes-sorted.txt

Be sure that your submission follows all homework submission requirements.