CSE 142 Spring'04

Assignment 2

Psychology Experiment

Due Dates:
BubbleMaker and LogoMaker classes due electronically Thursday night, April 15 at 10pm; paperwork (including "Prelude to Act II") in class (lecture) the next day. Should you print the receipts? The turn-in forms or the receipts themselves will tell you.

Final programs (experiment and trial series classes) plus text file, due electronically Wednesday night, April 21 at 10pm; paperwork in class (section) the next day.

Note: Exam #1 is Friday, April 23!

When you look at a geometric figure, does the shape or color influence how large you judge the figure to be? Psychologists investigate perceptual questions like this by running experiments in which people's reactions are observed, recorded and analyzed. In this project, you will use your new programming skills to set up experiments of this nature. As a preliminary step, you will implement two Java classes for practice.

Please read the entire assignment word for word all the way through before you begin. It is important to read the entire assignment through to the end, even the parts that are not due until much later. Compared with the previous assignments, you are not given as much detail about how to proceed. Try to understand as much as you can before beginning. However, you might not understand everything right away, some things may seem vague or incomplete. Don't let that bother you too much! Read and re-read. Ask questions. Try things. As you make progress things will eventually make sense.

Overture

The first part of this assignment is to investigate some library classes and methods. There is nothing to be turned-in from this part.

javax.swing.JColorChooser. The class JColorChooser in the Swing library of Java allows a user to select a Color. It has a static method showDialog. It needs three parameters, which can all be null (i.e., use the special keyword null), and returns a Color. Using DrJava's interactions pane, try calling this method (sending a message). (Don't forget to include an import statement before you try using JColorChooser). What happens? Can you figure out how to save the returned Color to use later? If you don't understand something, feel free to ask questions about it. Write a short (2-5 line) sequence of statements you can execute in the interactions pane of DrJava to demonstrate what is happening. For example, let the user choose a color, and then display a Rectangle of that color in a GWindow.

If you are curious about what the parameters mean, locate the documentation for the class (follow links from the menu bar of the CSE142 home page).Can you guess what might be good values for parameters two and three? (Leave the first parameter as null). Try things out. Experiment!

uwcse.io.Input. This class in the uwcse library has several methods for getting values from a user. Find the documentation. Try out all of the following methods (at least): readDouble, readDoubleDialog, readChar, readCharDialog. Take note of other methods which might be useful. Write short sequences of statements you can execute in DrJava to demonstrate what is happening with readDouble and readDoubleDialog. See if you can get the user to input a value which then you redisplay in an output message. If you type in a value of the wrong type, what happens?

uwcse.graphics.TextShape. This class is similar to uwcse.graphics.Rectangle and other shapes you have used. Try it out in the DrJava interactions pane. See if you can get your name to show up in blue letters in a GWindow. Can you change the color to yellow without creating a new TextShape object?

java.lang.Math. This class is mentioned several times in the textbook. Find the Java API documentation for it and browse a bit. Write a short sequence of statements in the DrJava interactions pane which calculates the following: given the area of a circle, what is its radius? Given the area of a uwcse Oval and its width, what is its height?

Act I

BubbleMaker. This is the first part you actually have to turn in. Create a class called BubbleMaker which knows how to draw small circles (bubbles) on a GWindow. Each bubble is green and has an area of about 2000 pixels.

Write a constructor for BubbleMaker which takes no arguments and displays a blank GWindow on the screen.

Write a method for BubbleMaker, named paintBubble, which takes two parameters, the desired x and y coordinates of the bubble (as pixels, exactly as for the shapes of uwcse.graphics) and adds a new bubble to the window.

Implement the BubbleMaker class and use the interactions pane of DrJava to try it out. That is, create a BubbleMaker object, and then call paintBubble (send a message to the BubbleMaker object) several times in a row to create bubbles at different locations on the window.

If you're not sure where to begin, work on BubbleMaker away from the computer. Start by writing the empty skeleton of a class (named BubbleMaker), on paper. If you can do that, add in specifications for the constructor and the method. Then add implementation code. Write as much or little as you can and then take your work to a course staff member, who can help you progress to the next step.

You will be asked to turn in the BubbleMaker.java file.   As mentioned above, it must have constructors and methods exactly as described -- you can't use other names or spellings, or change or add parameters, etc.

LogoMaker.   This is another class that will be turned in. A "logo" for this problem is a graphic consisting of a letter (single character) centered (more or less) inside a triangle. The top edge of the triangle must be parallel to the x-axis.

Stop reading now and draw a sample logo on paper, given the preceding short description.

The LogoMaker class helps a user design a logo. The logo is displayed in a GWindow. There is only one logo visible. Some of its characteristics can be changed, in particular: the letter being displayed, the size (area) of the triangle, the color of the triangle, and the color of the letter. Objects of type LogoMaker can display a logo on a GWindow, and also allow the user to select colors, choose the size of the triangle, and specify a letter. The location of the logo on the window cannot be changed by the user (the LogoMaker puts it somewhere appropriate).

LogoMaker must have the following methods and constructors. [Here, as elsewhere in CSE142 and in programming in general, a list like this implies certain things that must be followed exactly, and others that might leave you some freedom. For example, the name of a method is always assumed to be an exact, unchangeable requirement, case sensitive.   Other such absolutes include whether or not something is a command or query, what the return type is, and what the types of the parameters are. The order of the parameters is generally implied as well. On the other hand, the exact names of the parameters are rarely considered an absolute requirement when given in this style.]

a constructor (with no parameters) which sets the defaults as: blue letter, yellow triangle, size (area) 3000, letter 'X'.
a constructor which takes as parameters the letter color, the triangle color, the size (area), and the letter. The constructor parameters should be in the order just mentioned.
a command paintLogo, which paints the logo using the current values for colors, size, etc. Any past logo is erased first. The method has no parameters.
a command changeLetterColor which lets the user select a color for the letter, and which then repaints the logo (using the new letter color, of course). The method has no parameters. Hint: use JColorChooser.
a command changeTriangleColor which lets the user select the color for the triangle, and which then repaints the logo. The method has no parameters.
a command changeArea which lets the user specify the size (as pixels) of the triangle, and which then repaints the logo. The method has no parameters. For example, if the user wants the area to be 10000, and the triangle is equilateral, then what would the length of each side be? The user enters the size (area), and the program has to figure out dimensions and coordinates.. Hint: use one of the uwcse.io.Input classes.

Begin by writing down a Java specification for the class. That is, write a class definition which has specifications for all the items mentioned above. Add instance variables that you think you might need. Then begin to implement the methods, starting with the default constructor. If at any point you get stuck, or don't know how to proceed, ask for help immediately. The file LogoMaker.java will be handed in.

Prelude to Act II

You should not wait until Act I is complete before reading and thinking about Act II! To show that you have read and understood Act II, answer the follow questions (on paper). This will be turned in with with the paperwork for Act I.

Draw (freehand) a picture of the GWindow as it might look when a trial is being presented to the subject. Use colored markers (or write the color names in English). For that picture, what is a correct user input (answer)? Your picture doesn't have to be at all beautiful, as long as it captures the essential idea (i.e., it demonstrates that you know what is being asked).

Draw another such picture, different from the first, that could come from the same test series, and state what its correct input is.

Suppose the smaller area is 10000, and the "difference" (as defined in the instructions) is 15. If the smaller figure is a circle, what is its radius? If the larger figure is a square, what is the length of a side?

Act II

The experiment is to operate roughly as follows. Note that this is not programming specifications! It describes the people in the experiment and what they are doing:

The psychologist (person running the experiment, i.e., you) sets things up (chooses the colors, etc.).
The subject (person taking the test) sees a window with two geometric figures, side by side.
The figures have slightly different areas.
They may be different colors.
They may be different shapes.
The subject must decide which of the two figures is larger.
One trial is the presentation of the figures and the decision by the subject of which is bigger.
A trial series consists of the subject completing five such trials, each of which appears different (different shapes and/or colors, etc.). The experiment reports a summary of the results.

Implement the following classes and methods. You may notice that the specification for the classes above is less specific than for BubbleMaker and LogoMaker. You may find that additional methods or constructors are needed. You may decide that return values and/or parameters are needed for some of the methods. You will almost certainly decide that instance variables are needed in one or both classes.

class Experiment

Experiment (constructor): The constructor takes no parameters.
chooseColors: The psychologist chooses two colors to be used for the shapes in the trial series.
setAreaDifference: The psychologist specifies how close in area the two figures are to be. This is given as a number (double), which is the percentage difference between the larger and smaller figure. For example, if the difference is 10.0, it means that larger figure should be exactly 10% larger in area than the smaller figure.
reportResults: Using System.out, the Experiment object displays the results of the last set of trials, in particular:
-- how many trials there were
-- how many choices were correct
-- how many choices were incorrect
-- the percent of correct answers
-- the colors used
-- the percent difference in area
run: When this method is called, a complete experiment is run, that is, the psychologist is asked to choose parameters (colors, area difference), a trial series is conducted, and the results are reported. This is a command (no parameters).

class TrialSeries

TrialSeries (constructor): The colors to be used and the percent difference are given as parameters.
runTrials: Runs the complete series of trials. It makes a better experiment if the subject cannot guess the answers in advance. For example: don't use the same shapes every time. Don't always have the colors in the same order. Don't always have the larger figure on one particular side, etc. A single trial, as described earlier, consists of presenting the subject with two figures, asking the subject which is larger, getting the user's answer, and remembering the total right and wrong so far. There should be a message on the GWindow telling the user which trial is underway (1 through 5). The user should be told to enter the character 'L' or 'R'. Any response other than the correct character is considered to be a wrong answer. Be sure to clear the screen before each trial!
getCorrectCount: Reports how many correct answers have been recorded so far.
getWrongCount: Reports how many incorrect answers have been recorded so far.

When the classes are complete, the following lines of code, typed in the interactions pane, must be enough to run a complete experiment. When grading, no exceptions to this requirement can be made.
Experiment drPysch = new Experiment( );
drPysch.run( );

For this part of the project, you will turn in the two (separate) files, Experiment.java and TrialSeries.java. You will not be able to turn in additional Java files, or Java files with different names.

Note on robustness: A "robust" program is one that operates reasonably even in the presence of errors. For example, if the psychologist typed in an unreasonable value for the area difference (the number was negative, too tiny, or too huge, or a string was entered instead of a number) the program would notice this and let the user enter another value. For assignment 2, your program does not have to be robust! You do not have to check for bad data. If your program blows up because of an input error (as opposed to a programming error), it's OK -- this time!

Part 3 – Postlude

In this part of the assignment you will write about the work you have done. Create a new text document where you can put your answers to the following questions (You can use Notepad or some other text editor.) This file will be turned in. You must number each section of the file with the corresponding number of the parts below.

Run the experiment at least twice "for real". That is, get a couple of people who are not in CSE142 and let them go through the trials. Write down the results. Then write a short "lab report" giving the results and the experimental parameters (colors, difference, etc.). There is no special format for this report. One short paragraph, or perhaps a table, should suffice. It should include the date that the experiment was done and the names of the subject (or just their initiala), in addition to the experiment results.
Write one paragraph summarizing your experience working on the programming part of this assignment. You might mention positive things, frustrations, discoveries, or anything else you wish to share. If there was some part of the assignment you were unable to complete, please describe your difficulties with it.

Suggested Self-Study Exercises

As you go through the course, you should work as many of the Self-Study Exercises in the textbook as you can. The answers for all of them are given in the book. Here is a list of the problems we particularly recommend working.. If you can't get the answers on your own, feel free to discuss them on the Message Board, or come and talk to any of the course staff about them. (By the way, you may also find it helpful to work the other, non-Self-Study Exercises as well, even though the answers are not in the book. Any of these that are not assigned as homework are fine to discuss on the Message Board).

Note: Do not wait until the second week of this Assignment to do these! Chapter 4 is material we are covering in class during the first week of the Assignment period.

4.3, 4.4 (at least a-g), 4.5 (at least a-d), 4.5, 4.6, 4.8, 4.9, 4.11, 4.12, 4.13
12.9, 12.10

Turn in your homework using the turn-in form. These forms will be linked from the Assignments page before the deadlines. Read the forms carefully for further instructions or clarifications they may contain.

Playtime: Characters and Fonts

Just for fun! You don't even need to read this unless you run out of other things to do.

Unicode code pages. Figure out how to display a string or character in a non-Latin character set (such as Chinese, Arabic, Klingon, etc.). The Unicode character set used by Java is documented on the Unicode web site. Look for the "code charts" link then find the block of characters you want. Most blocks have the names of languages, but some are not so obvious (Chinese, Japanese, and Korean characters are scattered among several CJK blocks; the primary one is called "CJK Unified Ideographs"). Find the character you want and note its numeric value (ddddd).

In Java, you can indicate a Unicode character with the special notation \udddd. This goes inside single or double quotes, depending on whether you are after a Java char or a Java String. In DrJava you can use a TextShape in GWindow to display the characters (it almost certainly won't work on System.out). If you get a square box instead of a character, it means the default font used by TextShape doesn't know how to display the character. If you know a font on your system which does support Unicode, you can create a Font object and use the TextShape setFont method before displaying the character. Many Windows systems include Arial Unicode, which should work.