Design and implement a stringed musical instrument class

[andrew firth]

Design and implement a stringed musical instrument class using the following guidelines:
a. Data fields for your instrument should include number of strings, an array of string names representing string names (e.g. E,A,D,G), and boolean fields to determine if the instrument is tuned, and if the instrument is currently playing. You are welcome to add additional data fields if you like.
b. A constructor method that set the tuned and currently playing fields to false.
c. Other methods 1) to tune the instrument, 2) to start the instrument playing, and 3) to stop the instrument from playing.
d. Other methods as you see fit (Add at least one unique method).
2. Create a UML class diagram using a diagram tool (e.g. PPT, Visio) of your choice. Prepare the diagrams and place them in a word document along with a brief description of each of your classes.
3. Create Java classes for your instruments. Be sure that your code matches your design specifications and some minimal functionality is included. For example, if you called the violin.play() method, you should at least print that the violin is playing. Similar functionality should be supplied when you stop playing, tune or call any of your methods. For example:
public void playviolin() {
System.out.println("The violin is now playing.");
}
4. Write the output from your Instrument class methods to a text file that a user entered from the command line arguments (e.g. java Mynamep3tst myfilename.txt). This allows your program to accept filenames from the user via a command line argument.
5. Finally, create a Java test class that simulates using your instrument class. In your test class be you should at a minimum: a) Construct 10 instances of your instrument, b) tune your instruments, c) Start playing your instrument, d) Call your unique method, and e) Stop playing your instruments. (Hint: Arrays and Loops will make your job easier and result in more efficient code!)


Here is what I have so far, I seem to have an issue at the Violin violin1 = new Violin(); portion of the code and I am having difficulty figuring it out, please help! thanks!

package andrewfirthp3;

// Author AndrewFirth

public class AndrewFirthP3 {

    public static void main(String[] args) throws Exception
    {
        
        java.io.File file = new java.io.File("AndrewFirthP3test.txt");
        
        //check to see if file already exists
        if (file.exists())
        {
            System.out.println("File already exists");  
                System.exit(0);  
            }  
        
            //create a file  
            java.io.PrintWriter output = new java.io.PrintWriter(file);  
        
            //declare violin object  
            Violin violin1 = new Violin();  
               
            //write test results to file  
            output.println(violin1.playViolin());  
            output.println(violin1.stopPlaying());  
            output.println(violin1.tuneViolin());  
        }   
           
class Violin   
 {  
     boolean isTuned; //Violin starts off not tuned  
     boolean isPlaying; //Violin is not playing at start  
        
     //array for Violin strings  
     char [] violinStrings = {'E','A','D','G'};  
        
     //default Violin object  
     public Violin()  
     {  
         isTuned = false;  
         isPlaying = false;  
         System.out.println("The violin is not playing, and it is not tuned.");  
     }  
        
     public Violin(boolean T, boolean P)  
     {  
         isTuned = T;  
         isPlaying = P;  
     }  
        
     public boolean playViolin()  
     {  
        System.out.println("The violin is playing!");  
        return isPlaying = true;  
     }  
        
     public boolean stopPlaying()  
     {  
         System.out.println("The violin has stopped playing.");  
         return isPlaying = false;  
     }  
        
     public boolean tuneViolin()  
     {  
         System.out.println("The violin is being tuned!");  
         return isTuned = true;  
     }  
        
 }  
   
}  

[dennis deems]

Did you intentionally nest the Violin class inside the AndrewFirthP3 class? Since Violin is an inner class, it can't be instantiated unless (a) there is an enclosing instance of AndrewFirthP3 or (b) the Violin class is changed to be static. But I think this is not what you want. It's simpler just to define the Violin class outside the other class.

[andrew firth]

"It's simpler just to define the Violin class outside the other class."

I am trying to do this and getting frustrated with the process. What is the best way to do this without changing many lines of code around?

[Campbell Ritchie]

Welcome to the Ranch

You will probably have to move code, because you would want the Violin class to be public, so it needs to be in its own file. You can move the Violin class out of the other class simply by moving a few {s and }s.

[andrew firth]

thanks

[dennis deems]

If you want to keep the Violin class definition in the same file, then all you have to do is change the placement of a single brace.

Your file structure is currently this:

public class MainClass
{
    class AnotherClass
    {
    }
}

The structure you want is this:

public class MainClass
{
}

class AnotherClass
{
}

Edit: as Campbell says, it's better for Violin to be public.

[andrew firth]

thanks for the help

[Winston Gutkowski]

andrew firth wrote:I am trying to do this and getting frustrated with the process. What is the best way to do this without changing many lines of code around?

My suggestion (and the first one is the same as I give to ALL newbies here) is this:

1. STOP CODING, and turn your computer OFF.
2. Back up and look at the problem (and also whether you are looking at this as simply a programming exercise or a real music program). If it's the first, then simply write out, in detail, what it is you need to do. If you need to actually provide implementations for the methods, then do that too, ON PAPER, before you write another line of code.
3. Scrap what you've done so far, and start again.

Sorry if it sounds brutal, but in order to write code for a solution you must first understand it. Most of the best programmers I know spend 20% of their life coding (at the most). The rest is spent with bits of paper, whiteboards, or just down the pub thinking (at least, so they tell me).

If the problem really is to write a musical program, then "tune the instrument" strikes me as a major challenge right off the bat. The bloke who came around to tune my mum's upright had been doing it for 25 years when I knew him, and said there were still things that he didn't fully understand about the process.

Winston

[dennis deems]

Winston Gutkowski wrote:

andrew firth wrote:I am trying to do this and getting frustrated with the process. What is the best way to do this without changing many lines of code around?

My suggestion (and the first one is the same as I give to ALL newbies here) is this:

1. STOP CODING, and turn your computer OFF.
2. Back up and look at the problem (and also whether you are looking at this as simply a programming exercise or a real music program). If it's the first, then simply write out, in detail, what it is you need to do. If you need to actually provide implementations for the methods, then do that too, ON PAPER, before you write another line of code.
3. Scrap what you've done so far, and start again.

Sorry if it sounds brutal, but in order to write code for a solution you must first understand it. Most of the best programmers I know spend 20% of their life coding (at the most). The rest is spent with bits of paper, whiteboards, or just down the pub thinking (at least, so they tell me).

If the problem really is to write a musical program, then "tune the instrument" strikes me as a major challenge right off the bat. The bloke who came around to tune my mum's upright had been doing it for 25 years when I knew him, and said there were still things that he didn't fully understand about the process.

Winston

This is excellent advice in general. However, in this case it strikes me as a bit drastic. I see no problem in Andrew's Violin class, and it is very close to meeting the requirements of the assignment. You simply can't scrap everything you've done and start over every time you hit a rough spot.

[Winston Gutkowski]

Dennis Deems wrote:You simply can't scrap everything you've done and start over every time you hit a rough spot.

Oh g'won. 73 lines? Heck, I've trashed more than that in a lunch hour.

But I take your point (and perhaps you should too andrew (providing you heed the rest); all us old fart programmers are nihilists - probably something to do with growing up in the 60's).

Winston

[Campbell Ritchie]

Dennis Deems wrote: . . . I see no problem in Andrew's Violin class, . . .

You might not, but I do. I have gone down with a nasty attack of déjà vu. You will get even more déjà vu, Winston, when you see what I said last time I saw that code:

You need to start small. Comment out everything, write (or un-comment) 5 lines, compile and run. Repeat the process until the class is complete.

The code shown here is virtually identical to the other code I saw.

[dennis deems]

Campbell Ritchie wrote:

Dennis Deems wrote: . . . I see no problem in Andrew's Violin class, . . .

You might not, but I do. I have gone down with a nasty attack of déjà vu. You will get even more déjà vu, Winston, when you see what I said last time I saw that code:

You need to start small. Comment out everything, write (or un-comment) 5 lines, compile and run. Repeat the process until the class is complete.

The code shown here is virtually identical to the other code I saw.

I remembered seeing the exercise before, but I hadn't recognized the code. You have a sharp eye, it is indeed virtually identical.

[Campbell Ritchie]

The only differences are the misplaced {} and the different student’s name. I hope he hasn’t handed in what he posted, because it will earn him a 0 for plagiarism