Questions on HW3-Summer07

Questions on HW3-Summer07

Ask Questions on homework 3 here. Please enclose code with <code> </code> tags.

Question: How can you make the turtles pause when moving in the world?

It's sometimes easier to think of a Turtle as a little robot that does everything you tell it to do. One way to get the Turtle to stop moving is to simply not give it any commands to move, but let us say you want the Turtles to pause while the "music" (or bunch of Sounds) is playing. Instead of using just plain play(), you can use blockingPlay() which basically tells everything else to pause while the "music" is playing. Dawn Finney.

Question: When I am trying to

import jm.JMC;

it keeps saying

ClassNotFoundException: jm$JMC

what does that MEAN???? i downloaded Jmusic and i thought everything went right. not really sure what to do.

Remember when we added those extra classpaths in the DrJava's preferences back when we were first setting up? Did you remember to add one for jmusic.jar and one for the inst folder? More importantly you know that we expect you to use Sounds for this homework and not music, right? Dawn Finney.

Question: crap, what's the difference between sounds and music?

Sounds you use the Sound objects. Music you use the JMusic package and make Songs, Notes, Parts, etc. It's basically the difference between MySoundCollage.java and AmazingGraceSong.java. Technically you can use the JMusic stuff for this homework, but we really want you to use Sounds 'cause it's easier to just use Sounds. Dawn Finney.

Question:What does the error "class" or "interface" expected mean?? I wrote a method in Turtle.java to make the turtle do a specific dance so that way i could just use turtle1.dance, turtle2.dance..etc but when i compile the code, i get the above error.

You probably put the code outside of the class declaration (after the closing curly brace). Dawn Finney.

Question: On Tsquare, what is the difference between submitting on the "assignment" page vs submitting it under the Assignment "auto submission" page?? Which one should we use?

I honestly have no clue. T-square is just as foreign to me as it is to you. When in doubt, email your homework! Dawn Finney

Question: Even though I added extra classpaths in the DrJava's preferences, every time I try to

import jm.music.data.;
Error: C:\cs1316\java-source-Fall06\Song.java:1: package jm.music.data does not exist

comes out. What should I do?

Honestly the only reason I can think of that your classpaths are set up incorrectly (I know a girl said that the one I set up for her isn't working either, but hey I'm not totally infallible). Make sure you have classpaths pointing to jmusic.jar and the inst folder. If you just have it point to the folder containing both jmusic.jar and inst, it will not work. Dawn Finney.

QuestionWhat is the method to use to get the song to play. I konw you can use node.showFromMeOn() and it brings the notes up and you hit play but I want it to start playing automatically when i run my code. Is there a node equivalent of song.play();?? I hope that question makes sense

"I recommend using the a modified version of SongNode.java that I have written specific to this homework. You can review the java doc. Basically I added a method playFromMeOn that will play your music automatically and does not use the note viewer. I also added a method blockingPlayFromMeOn that works like blockingPlay from Sound" from homework 3 description. These methods also should have been mentioned and explained during recitation. To answer your question more specifically playFromMeOn is basically like play. See Recitation Guides-Summer 2007 for past recitation guides. Dawn Finney.

Question: When it says to turn in the picture of the resultant list structure, what do we use to make that??

"Draw a picture of your resultant list structure. Show us where all the nodes are in your final composition. You can do this by drawing with a tool like Paint or Visio or even PowerPoint, or you can draw it on paper then scan it in. You can turn in JPEG, TIFF, or PPT files" from homework 3 description. Honestly reading the homework description won't kill you and you won't have to endure sarcastic comments from me either. Dawn Finney.

Where could I draw my daily entertainment if I didn't have the benefit of your sarcastic comments?

Yeah, that could be quite a problem. Dawn Finney.

Question: I have a really basic question. Do you declare/define your turtle objects and riff objects BEFORE you start your main method or in the body of the main method? In general, I'm not clear how the main method should relate to other methods and objects. (And please say something sarcastic in response for my amusement...)

You can think of the main method as a sort of testing ground for your code where instances are born so to speak. The interactions pane in Dr. Java is basically a substitute for a main method. For this assignment, your Turtle and riff objects should probably be declared in the main method, but in general they could be declared in a number place depending on what you ultimately want to do. Dawn Finney.

More basic and related questions: 1) after you create your SongNodes, do you then need to create a linked list data structure from these?, or 2) do the operations on the SongNodes CREATE the list structure (rather than operating on an original, specified one)?, and 3) do these operations (that is, weave, repeatNext, or repeatNextInserting) operate on the product or output of the previous operation, so that a resultant woven list, for example, is then used to insert new phrases in the next operation?, and 4) do these operations act in the sequence in which they are specified in the program?, and, finally, 5) if you have methods that manipulate the phrases and control the dance of your turtles both placed in the main method (assuming that is correct to do), are these, in effect, implemented in parallel? I guess I am generally confused about the nature of the control structure in this object-oriented hocus-pocus. Can we go back to structured programming? ;)

Yes. After declaring your SongNodes, you must then link them together to create linked list.
It really depends on how you want to do it. I would go ahead and create a basic list and then use weave and either repeatNext or repeatNextInserting to add extra nodes to it.
These methods operate on (sometimes creates) the list itself. I don't really understand the example you stated.
The lines in the main method always execute from top to bottom.
I guess this part has to do more with whether or not the turtle dance and the music will occur in tandem. When you put the line of code to play the music before your turtle movement, Java executes the line to play the music but will move on before the music finishes, because you only really asked it to play the music. Though this may all seem to be some type of witchcraft, I do assure you that it works and encourage you to test it yourself (well you kind of have to if you want to get all points for your homework)

I hope I answered all of your questions. Dawn Finney.

The documentation for the repeatNext method says that it appends the input phrase to the "current" node. What is the current node in this context? The last node of the previously transformed linked list?

The current node is the node that is being called on by the method. Let us say that if you did
```
node1.repeatNext(node2, 2);
```
The method repeatNext is being called on the object node1, thus node1 is the current node. Dawn Finney.

Question: Please remind me how to slow the progress of turtles moving in a world so as to make the motion visible. Thank you.

There are two ways to do this. One is to put in a call to Thread.sleep(). Use the predator/prey example that I posted to the syllabus page as an example. Unfortunately, this technique requires that you use try/catch, which is a more advanced construct than we want to deal with in this class. If you can get it to work, just treat it as a Java incantation. The second method is to use a sleep argument for FrameSequence.replay(). Check the Javadoc documentation for that. Both approaches use milliseconds as the unit of time. Colin Potts
I agree that the first way to do this is to use Thread.sleep(). You could also use the new method I wrote called blockingPlayFromMeOn that works basically like blockingPlay from Sound. FrameSequence is so incredibly slow. OMG. Dawn Finney.

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Homeworks-Summer 2007 last edited on 21 July 2007 at 10:06 am by adsl-154-122-133.asm.bellsouth.net