Questions on HW2-Spring08

Questions on HW2-Spring08

Ask questions on homework 2 here:

When we did turtles in Python, we were taught how to import time, so we could make the turtles move slowly. I'm having trouble with my code to make a curved letter, and if there was a way to do that in Java, so I could see what the turtle is doing.

At this point in the course, I would suggest using the debugger and breakpoints. A breakpoint is a flag in the code that tells the debugger to stop execution of the program. When your program stops on a breakpoint, you can examine the value of variables, single-step through your program, examine the state of your program, and so on. Dawn Finney.

Question: I've recently been getting an error on every code I write that does not recognize the class...am I missing a program or something?

Error: cannot find symbol
symbol  : class World
location: class LetterTurtle

Go find World.java and compile it. Dawn Finney.

Question: I made the J in my name by creating a straight line, and then a semi-circle from 0 - PI clockwise. While this seems to work, and I have made a J, I think trying to connect two PI/2 - 3PI/2 semi circles to make my S may be a bit "caveman-like". Is there a smoother way to create such letters?

We technically don't have to help you with the bonus at all. You'd have to bug a kind TA during office hours or via email. :P Dawn Finney.

Question: Is it enough credit to make an I with just a vertical line, or do I need the top and bottom horizontal lines? If I need the latter, how do I move to a position that is half of int x, because whenever I plug in an odd number to run the method, it cuts off the decimal, so the vertical line is not centered. Is there a way to make the moveTo function to take in a double?

I don't know. Can you live with yourself if you just did an I with just a vertical line? Um half of int x? You know that int x is a coordinate right? And not a width. Dawn Finney.

Question: When I searched simpleTurtle for a pen width method, I found:
public void setPenWidth(int width) {
pen.setWidth(width);
However, when I use the method in my LetterTurtle, it says: pen has private access in SimpleTurtle
Indeed, in Pen, the width method is private. I tried creating a new object prior to the pen.setWidth command by putting Pen p = new Pen(); , and while that compiled (with a warning), the pen width still did not change. Ideas?
I can't seem to get the pen width adjusted. I looked in the Pen.java file for the command, but I'm not sure which one to use? setWidth? Or maybe I'm putting it in the wrong portion of my code?

Use the setPenWidth(int width) method from SimpleTurtle. Dawn Finney

Question: The HW says that the final result cannot contain a visible turtle. Since the picture is supposed to appear in a World, is there any way to get rid of the turtle, aside from making the pen width large enough to cover the turtle?

Look around at any visibility methods that may be in Turtle or SimpleTurtle. I believe there is something called setVisible(false). Joel Uthe
The method is hide(). Dawn Finney.

Question: I keep getting an error that is expecting ";" when ";" is obviously there... and it can't find the method circle, even though I copied the exact same circle code from class

Check the line before for the semicolon error. You're probably calling the method wrong or something. Hard to tell without more detail. Dawn Finney.

Question: My program compiles only if the Turtle.java is also open. Can I assume that the TAs will have Turtle.java open or do I have to import it somehow in LetterTurtle.java?

It is possible that your classpath isn't set up correctly. TA's will have their classpath's set correctly, but will not have Turtle.java open when they grade. Joel Uthe

Question: I just used the method setVisible(false) to hide the turtle and it worked. Do I have to change it?

You can use either method. Joel Uthe

Question: I read the above answers about pens, and I followed the advice, but I still keep getting errors that say SimpleTurtle has private access. This is what I'm trying to do:

  public void setPenWidth(int width){pen.setWidth(width); }

What am I doing wrong? It's between my main method and the other methods.

You shouldn't be copying other methods from parent classes into your code. The beauty of inheritance is that it will automatically look in the parent class. You can use the setPenWidth method w/o copying the method itself into LetterTurtle. Joel Uthe

Question: For the extra credit, could the lower-case version of a letter count?

The extra credit is more about quality. If it is a really good letter then you should receive credit. Joel Uthe

Question: I cant call the methods I create for drawing the letters. When I try to do this in the main method after creating a turtle ("fred.writeB(100,200)") I always get an error message telling me the symbol cant be found. Are we supposed to create the turtles in the main method? If not, how??

Yes you are supposed to create a new LetterTurtle in the main method. It's likely that you just have some simple syntax error in your code. The best way is to have a TA look at it (now you could only do it via email) or you could try giving more details here. Dawn Finney.

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Homeworks-Spring 2008 last edited on 14 April 2008 at 11:35 am by lawn-128-61-18-61.lawn.gatech.edu