An error that I don't get

Question

Hi,
Below is a member that is supposed to play an audio clip. The debugger complains about the line in the second try statement. The error messsage says: "variable clipURL might not have been initialized". What is wrong? Didn't I just initialize clipURL in the preceeding statement?
public void Play(JPanel[] channels){
        Clip clip;
     AudioInputStream audioInputStream = null;
        java.net.URL clipURL;
        try{
            clipURL = new java.net.URL("File:C:\\Documents and Settings\\Pingen\\Desktop\\sound.wav");
        catch(Exception e){
        try{
            audioInputStream = AudioSystem.getAudioInputStream(clipURL);       //Here is the line I'm talking about.
        catch(Exception e){
        AudioFormat format = audioInputStream.getFormat();
        DataLine.Info info = new DataLine.Info(Clip.class, format);
        clip = (Clip) AudioSystem.getLine(info);
        clip.open(audioInputStream);
        clip.start();
    }Regards,
Pingen

Answer 1

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The debugger complains about the line in the second try statement. The error messsage says: "variable clipURL might not have been initialized". What is wrong? Didn't I just initialize clipURL in the preceeding statement? No, because if an exception is thrown in the first try block, then control might have flowed to the catch block before clipURL has been set.
By the way:
1) Don't have empty catch blocks like that. At the very least, put this in:
e.printStackTrace();If something goes wrong, you need to know about it!
2) You haven't structured the flow of control well. What if the URL is bad and you end up with a bad or null clip URL. Do you really want to try to get the audio output stream from it? Suppose you can't get the audio output stream, do you really want to try to play the clip?
The whole point of try/catch blocks is to help you recover from errors, but you've set it up so you don't recover, you just keep plowing forward.
Ask yourself how you'd recover from an error at any particular step that might throw an exception. Then you could restructure accordingly. For example, if any exception leads to "just do nothing, and don't affect the calling method", then put all the code in a single try block, and have a single catch block that just prints an error message. If a bad URL means that you'd rather play a default clip, then set that default clip's URL in the first catch block.