CSE 341 -- Programming Languages

Autumn 2001

Department of Computer Science and Engineering, University of Washington

Steve Tanimoto (instructor)

Assignment 5

Version 1.0 of November 16 (Subject to Change)

A Sip* of Java

Due date and time: Wednesday, November 21, 2001 (at the beginning of class).

Turn in this assignment by putting all your files in a subdirectory of your cubist www directory, named a5. You should have a web page (containing your applets) named index.html in that directory.

Title: A Sip* of Java

Purposes: 1. Learn about how Java handles class structure, inheritance, component accessibility and various other language issues. 2. Gain practice creating applets.

Instructions: Read Chapters 1-9 of Learning Java.

Part A: Applications
1. (Simple, imperative coding in Java.) Write a Java application that prints out the first 50 Fibonnaci numbers.

2. (Working with inheritance and info hiding) Write a Java application that constructs several instances of 3-D figures as software objects and prints out their descriptions by invoking their describe methods. Use the following guidelines:

add four new classes to the class hierarchy shown in class on Nov. 7. One of these classes should be 3DFigure (or ThreeDFigure) Another should be HybridFig (or MixedFigure) and one should be Cylinder. The last one should be Sphere.

make decisions about what methods should be abstract and what should be concrete. Justify each decision.

Decide whether your data members should be public, protected, package, or private, and justify your choices.

Document your code with comments in the code.

Part B: Applets
3. (Basic applet structure) Write a Java applet that determines the nth fibonnaci number by letting the user enter an integer (n) in a text field and then click on a button labeled Nth Fib.No. It should then draw the number on a drawing area (such as a JPanel or a Canvas) under the text field and button. Put the applet on a web page and turn in both a URL to the web page and hardcopy of your code. You can put the web page in your Cubist account, in your www subdirectory.
Optional variation 1: instead of returning the Nth Fibonnaci number, return the nth Prime number. In this case your button should be labeled Nth Prime.
Optional variation 2: return not a number but a string that spells the number out in English words. For example, if the user enters 365 and clicks the button (labeled "to English words"), it should display "three hundred sixty-five". You should handle numbers up to 999,999.

4. (Applets and Inheritance) Choose one of the following two options.

Write a Java applet that defines several classes of "EmpoweredNumber" objects in a hierarchy and does operations on them including arithmetic operations of addition, subtraction, multiplication, and division. These numbers should also be able to display themselves and describe themselves. Empowered numbers are similar to natural numbers, integers, rationals, reals, except that they have these extra capabilities of telling about themselves and commenting on any particular contortions they may be asked to take part in. The user should be able to request operations on empowered numbers by entering type and value information and request particular operations. Make your class hierarchy come to life by giving the various types of numbers some personality. The following is just a suggestion for what this might be like.
```
User selects Natural and types in 59 + 0   and clicks "Compute".
Applet responds:
  This is 59 speaking.  I'm insulted to have a ZERO added to me!
  Hi, my name is Nought.  See how easy it is to count me in!
  OK. 59 again. At least I didn't have to change.

User selects Real and types 3.1 * 5.7 and clicks "Compute".
Applet responds:
  I'm 3.1, and you might be confusing me with Pi, who is a friend of 
mine.
  It's 5.7 here. I love to participate in REAL multiplication!
  This is 17.67.  I'm happy to have been produced.

User selects Natural and types in 5 - 6 and clicks "Compute".
Applet responds:
  I'm a natural 5.
  And I'm a natural 6.
  Hello world, I'm -1, an Integer.
```
It's up to you to decide what the numbers "say", but ideally their comments may take into account their values, their types, what operations they are participating in, and possibly the value(s) of the other operands. This behavior should be defined to take advantage of your inheritance hierarchy, so that if no special behavior is available for one type of number, then it inherits something appropriate from its parent.
Use your imagination. Show that you understand inheritance and can take advantage of it.
Write a Java applet that uses a class hierarchy of two-dimensional geometric figures to create designs. Suggested types of figures include Figures, Points, Lines, Segments, Ellipses, Circles, and Polygons. It should be possible for the user to cause the creation of any of these, perhaps by making a choice and then clicking on a canvas. Inheritance should be used heavily to emphasize the relationships among the classes.

* "Sip of Java" -- All right, perhaps we should have called this "A Single Short Latte."

Group Work: This assignment should be performed individually (not in groups).