Questions on HW1-Spring07

Questions on HW1-Spring07

Question: I put my method into the Picture.java file and the only error that keeps coming up is: 'class' or 'interface' expected. I followed the instructions from the book but it keeps bringing up this error and I dont know what it means or how to fix it.

Make sure that you have a class declaration in your Picture.java file and then put your method into that class declaration. You should also have a main method used to run the manipulation method you made in the class declaration. -Sarah Tursell
We'll be going over how to create methods tomorrow (17 Jan) in lecture. Mark Guzdial
REMOVEDces are you have unbalanced curly brace. Make sure that each method has an opening and closing curly brace, and also your loops will need them as well. DrJava will do some highlighting for you to help you find extra/needed braces. -Joel Uthe
Sounds like you placed your method outside of the class declaration (after the last curly bracket closing the entire class). Just move your method into the class declaration (before the last curly backet). -Dawn Finney

Question: What does it mean that we cannot use other methods for our HW assignment. can we use the simple methods such as length, etc or do we have to create those???

No, it means no other methods in Picture. So you can't call decreaseRed, for example. Mark Guzdial
Basically what Prof. Guzdial means that you can't have your method call another method in Picture. This prevents people from turning in methods like the following:
```
public void myDecreaseRed(){
   decreaseRed();
}
```
But you are more than welcome to use the methods already in Picture.java as a guide (in fact we encourage it). -Dawn Finney

Question: Just wondering where in Picture.java i should put my methods and what i should name them so the TA knows those methods are the ones i created? Jonathan

There is no requirement on the names of the method, but they must be at the BOTTOM of the class (after all the given methods). You can name them anything you want and just put a comment up at the top of the assignment saying what you named them. - Joel Uthe

Question: Can our method return something? Laura

It isn't against the rules for your method to return something, but it is not necessary. If you look at some of the methods in Picture.java, such as .scale(..), they return a Picture. But a method that acts similar to this will not fulfill the requirements. Your method must actually act on the picture itself <The picture that gets manipulated should be the target that receives the method (i.e., this). For example, if you implement the method "mytweak()", then you'll use it on some picture somePicture.mytweak(), and you'll expect the picture somePicture to change. (Don't bother returning a DIFFERENT picture for this method.)> is the exact wording in the homework. -Joel Uthe

Question: I've created my method in the Picture.java file – but I can't seem to use the method... actually I can't even declare a new Picture p variable – Dr.Java just keeps saying "Error: Undefined class (blah blah)"... for EVERYTHING!

It sounds to me like you're not compiling your source code. To do this, open up Picture.java in Dr. Java. Go to Tools->Compile Current Document. Then try. -Derek Olejnik
Like Derek said you might just need to compile Picture.java. If you ever encounter an Undefined Class Error, find that class in question (if you can't find it then it really is undefined, so you might want to define it) and compile it. -Dawn Finney

Question: Drjava works but it can't find the java-source.

I have added it in preferences and hit apply but it doesn't seem to be working. Any suggestions?|

Uh java-source is not still zipped right? It can't find the java source as in you get a bunch of undefined class errors? I'd need more info to answer this one. -Dawn Finney

Question: After compiling my method I get the error: "reached end of file while parsing" on the last line of my method - which is just a parenthesis. What could be the reason for this error? How can I correct this?

~Darshini|

You should start and end methods with curly brackets. I hope that is your problem. Else include the line in question and error Dr. Java gives or you could always email the entire method to a TA for advice. (Don't post the method here.)-Dawn Finney

Error: No 'makeReallyWhite' method in 'Picture' with arguments: ()
I keep getting this for my function after I do >p.show() and then try to do >p.makeReallyWhite()
I did save Picture.java after I wrote my function out.
I compiled at the very beginning also.

Your function might actually take in some parameter. If you want your method makeReallyWhite() to work without taking any parameters make sure your function header looks something like
```
public void makeReallyWhite()
```
-Dawn Finney

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Homeworks-Spring 2007 last edited on 19 April 2007 at 10:45 pm by c-76-17-114-206.hsd1.ga.comcast.net