©2006 Felleisen, Proulx, et. al.
Familiarize yourself with the Java Application Programmers Interface (API)
Learn the basics of working with the Java Collections Framework
Use exceptions to detect and handle errors
Download the provided zip file and unzip it. Create a new Eclipse project named Lab11. Add the given code to the project and link the external JAR jpt.jar to the project. Also add the SimpleTestHarness.jar. You should have the following Java files:
class Examples that is to be used for tests that are not a part of the program that interacts with the user
class Interactions that controls our user interactions
- you will add a couple of methods here
class Reply - a skeleton, you have to add the functionality
class SampleEliza the database of answers and some of
the methods dealing with the answers to the patient.
Go to the Java API at http://java.sun.com/j2se/1.5.0/docs/api/. Bookmark this page! When coding you will often use classes that are provided for you by Java. The Java API describes these classes and lists all of the fields and methods of these classes that are available to you.
The front page of the Java API lists all of the packages provided by Java. A package is a collection of related interfaces and classes.
The left frame of the API page lists all classes alphabetically. If you want the specifications for a specific class you can click in this frame and use your web browsers search function to find that class. For example, find the ArrayList class. Another way to quickly find Java API specifications is to search Google for "java api class x", where x is the name of the class you're searching for. For example, the search "java api class arraylist" returns the specifications for class ArrayList as the first result.
All of the specifications are in a JavaDoc format. JavaDocs are automatically generated from source code based on specifically formated comments that the programmer adds for each class and each method. We won't cover the format of such comments here, but it's pretty easy to do yourself. For more details, see How to Write Doc Comments for the Javadoc.
Lets use the ArrayList JavaDoc as an example.
The top of the JavaDoc lists the other classes that ArrayList extends and implements. In this case, ArrayList extends from the classes Object, AbstractCollection, AbstractList, and implements the interfaces Cloneable, Collection, List, RandomAccess, Serializable.
Next is a general description of the class. In this case, the JavaDoc says that ArrayList is a "Resizable-array implementation of the List interface."
Following this is a summary of fields, constructors, and methods provided by ArrayList. In general, classes will provide very few public fields and the JavaDoc will contain mostly specifications of methods. Look over some of the methods provided by ArrayList. We will be using a similar classes when cover the Java Collections Framework in activity 3.
The method summaries provide headers (return type, name, and arguments) and a short description of the method's functionality. More detailed descriptions are linked from these summaries and appear farther down on the same page.
The class Words contains some Strings and ArrayLists of Strings that we will use. Our first task is to reverse the order of the words in the ArrayList reversed. Design a method in the Interactions class that reverses the order of the words in the ArrayList.
Do the following three tasks - modifying the previous solution as you go on (or keeping the previous one and adding a new variant:
First just produce another ArrayList with the words reversed.
Next think of how you would reverse the elements in an ArrayList without using another ArrayList at all.
Finally, think of how you can modify the actual values of the ArrayList reversed in the class Words.
Finally, pring all words, one to a line, traversing the ArrayList using the for-each loop that uses the Java Iterator.
The text in the ArrayList words in the class
Words is encoded. It represents verses from a poem - if you
read only the first words.
Look up the StringTokenizer class in JavaDocs. The methods
there allow you to traverse over a String and produce one
word at a time delimited by the selected characters. Read the
examples. Then write the method makeWords that consumes one
String and produces an ArrayList of words.
Design the method firstWord that produces the first
word from a given String.
If you have not done so already, modify it, so it would recognize additional delimeters besides the default ones. Specifically, you want to recognize comma, semicolon, and the question mark.
Our goal now is to train our computer to be a mock psychiatrist, carrying on a conversation with a patient. The patient (the user) asks a series of questions. The computer-psychiatrist replies to each question as follows. If the question starts with one of the following (key)words: Why, Who, How, Where, When, and What, the computer selects one of the three (or more) possible answers appropriate for that question. If the first word is none of these words the computer replies 'I do not know' or something like that.
Start by designing the class Reply that holds an
ArrayList of answers to a particular question, and contains
the method randomAnswer that produces one of the possible answers
each time it is invoked. Make sure it works fine even if you add new
answers to your database later.
Next look at the class SampleEliza. This is our
collection of answers. We are giving you just a few - you can add
more as you wish. The field replies is defined as
HashMap. Look up the JavaDocs for HashMap. Ask
questions, if you do not understand. The design is similar to the
IMapping interface we worked with in our earlier homeworks.
Our goal is to select the right instance of the Reply
class each time the patient asks a question. The method
get(K key) produces the correct Reply, if it
consumes one of the keywords. However, it produces null if
there is no value corresponding to the given key.
The method findReply that is provided consumes a
String and produces a reply. Here the reply just parrots
the question: You asked .... Modify the method so that it
first extracts the first word of the question, then uses it as a key
to identify the possible set of replies from the HashMap of
replies and finally produces the answer. Of course, we already have
helper method for each of these steps.
We now have to make sure the program does not crash when the
user asks a wrong question. Add try-catch clause to the method to
catch the NullPointerException and reply 'I do not know' to
an answer it cannot identify. An example of how to catch an
exception is given in the method readAndWrite in the
Interactions class. Use also as the model for your final game
control method.
You can now play the game, using the playEliza method in the
Interactions class.