Mini-Lab: Using the Comparable Interface

Getting Started

Create a new project, and create new classes, replacing their contents with the code in the following files:
Looking over these files, you should thoroughly understand the ComparableMLApp class, and see that the SearchDriver and BinSearcher classes are very similar to classes we have already seen. The BinSearcher class, though, will do a binary search through any list of Comparable objects, not just Strings. In fact, the SearchDriver is currently set up to use the same BinSearcher object (an instance variable) for both String and Student objects.

NOTE: In lab, you will be turning Student, Bird, StoreItem, and Recipe into classes that implement Comparable, and then running tests on them from the SearchDriver. You will only modify the concrete list item classes ( Student, etc.) and SearchDriver. You DO NOT NEED to modify ComparableMLApp or BinSearcher.

Before you can run the program, you will have to complete the Student class. (Or comment out the code in the runBinarySearchTests method in the SearchDriver class that creates the Student list and uses Student objects.)

Student Class

Comparisons of students will be based on names; in other words, if student A's name comes before student B's name lexicographically, then student A will come before student B. We will also assume that student names are unique (no two students have exactly the same name).

Go into the Student class and specify that it implements Comparable<Student>.
Look at the constructors. The Student class has two constructors, but rather than include almost the exact same code twice, we are calling one constructor from another. The way to call a constructor from within another constructor in the same class is to call this as if it's a method. (This is a new use for the this keyword.) You do not need to modify the constructors unless you decide to add new instance variables to the Student class, but you should look them over and understand them.
Look at the toString method and make sure you feel comfortable with it. (You do not need to change it, although you may change the formatting if you want to.) Note that a class's toString method does not need to include all the information about an object; just enough to identify it.
Implement the compareTo method. Since the comparison will be based on names, return what a comparison of this object's name and the other object's name would return. Remove the "CODE MISSING" comment since there shouldn't be any code missing anymore.
Test your code with the tests that are already in the SearchDriver class.

Understanding the test driver code:
- Did you expect the first two tests ("beans" and "rutabaga") to behave as they did?
- Did you expect the first Rey Diaz test to behave as it did? Why do the two lines of output show different ID's? Read the code for the private searchAndReport helper method to understand what is going on. When is it printing information from the parameter, and when is it printing information from the object found in the list?
- Why does the second Rey Diaz test show different majors? Did you expect this test to behave as it did? If you didn't expect this, look again at your compareTo method in the Student class to find the explanation.
- Why does the code create an incomplete Student object using the one-parameter constructor rather than just pass "Rey Diaz" as the first parameter? (The answer to this might become more obvious after you do Birds.)
Add a few more students to the createListOfStudents method (remember that students should be sorted by name in the list because we're doing a binary search!), and then, back in the public runBinarySearchTests method, call runBinSearchTests a few more times to test the code more thoroughly.
What are good test cases? A common test is to search for some item in the middle of the list. Good tests would also include:
- search for the first item in the list
- search for the last item in the list
- search for an item not in the list
These are called boundary conditions or boundary tests.

Bird Class

Next, write a Bird class for tracking banded birds by ID numbers. Bird comparisons will be based on band numbers.

Specify that the class implements Comparable<Bird>.
Implement an accessor method that returns the band number (and other accessors if you want).
Implement the toString method (include the band number & species).
Uncomment the equals method. Notice how the equals method for Bird is different from the equals method for Student. Why is that? Is the difference relevant to compareTo?
Uncomment and implement the compareTo method. You will need to test equality separately from less-than/greater-than. (Or you can implement the entire method with one subtraction statement.)
There should be no CODE MISSING lines when you're done.
Uncomment and run the tests that are in the SearchDriver's runBinarySearchTests method. Add some additional tests. (You may also add more birds to the createListOfBirds method if you like.)

StoreItem Class

Write a StoreItem class to keep track of items in a store. Decide what store items should be ordered based on. (For example, name? Price?)

Specify that the class implements Comparable<StoreItem>.
Implement a constructor that takes a single parameter (the value you are going to search on). This could be the name parameter, as given, or you could change it to a price parameter and then set the name to an unknown name.
Implement an accessor method that returns the value you are going to compare (and other accessors if you want).
Implement the toString method (include at least the item name and id).
Implement the compareTo method.
Uncomment the equals method. If you do your comparison on an attribute other than name, change the equals method to use the same attribute. In other words, if compareTo is based on price, then equals should be based on price also.
There should be no CODE MISSING lines when you're done.
Create and run tests in the SearchDriver's runBinarySearchTests method.

Recipe Class

Create a new Recipe class. (Or some other class of interest to you, whose objects you could put in a list.
Decide what field recipes should be ordered based on. (For example, name? Contributor?)
Specify that the class implements Comparable<T> (where T is Recipe or whatever class you created).
Implement an accessor method that returns the value you are going to compare (and other accessors if you want).
Implement the toString method (include at least the recipe name and id).
Implement the compareTo method.
Create and run tests in the SearchDriver's runBinarySearchTests method.