Try catch confusion

[Ravaa Bal]

try
          {
             Sequencer sequencer = MidiSystem.getSequencer(false);
          }
          catch (MidiUnavailableException e){//stacktrace}

This bit code is giving me the error "';' expected", and the statement inside the try catch block doesn't recognise that I'm trying to catch the exception that it wants caught. Not sure what I could be doing wrong...here's the full class in case that gives more of an idea:

private class AccompanimentTransmitter implements Transmitter
     {
          try
          {
             Sequencer sequencer = MidiSystem.getSequencer(false);
          }
          catch (MidiUnavailableException e){//stacktrace}
     
          public void close(){
             //
          }

          public Receiver getReceiver(){
              return...;
          }

          public void setReceiver(){

              MidiDevice player = new Player ();
         
              try
              {
                  sequencer.getTransmitter().setReceiver(player.getReceiver());
              }
              catch (MidiUnavailableException e){//stacktrace}
          }
     }

Thank you in advance!

[Joanne Neal]

// comments out everything to the end of the line, so your closing } is also commented out.

[Rob Spoor]

Ravaa Bal wrote:

private class AccompanimentTransmitter implements Transmitter
     {
          try
          {
             Sequencer sequencer = MidiSystem.getSequencer(false);
          }
          catch (MidiUnavailableException e){//stacktrace}

That's a statement directly in a class, and that's not allowed. A class can only contain declarations - fields, methods, inner classes, etc - and blocks. So you can fix this as follows:

private class AccompanimentTransmitter implements Transmitter
{
    {
        try
        {
            Sequencer sequencer = MidiSystem.getSequencer(false);
        }
        catch (MidiUnavailableException e) { /* stacktrace */ }
    }
// rest of the class
}

[Ravaa Bal]

Aha! Thank you both, that explains a lot.

[Muhammad Ali Khojaye]

Ravaa Bal wrote:

try
          {
             Sequencer sequencer = MidiSystem.getSequencer(false);
          }
          catch (MidiUnavailableException e){//stacktrace}

This bit code is giving me the error "';' expected", and the statement inside the try catch block doesn't recognise that I'm trying to catch the exception that it wants caught. Not sure what I could be doing wrong...here's the full class in case that gives more of an idea:

private class AccompanimentTransmitter implements Transmitter
     {
          try
          {
             Sequencer sequencer = MidiSystem.getSequencer(false);
          }
          catch (MidiUnavailableException e){//stacktrace}
     
          public void close(){
             //
          }

          public Receiver getReceiver(){
              return...;
          }

          public void setReceiver(){

              MidiDevice player = new Player ();
         
              try
              {
                  sequencer.getTransmitter().setReceiver(player.getReceiver());
              }
              catch (MidiUnavailableException e){//stacktrace}
          }
     }

Better if you use the same code format style.

Style 1

try
{
//code
}
catch(MidiUnavailableException e)
{

}

Style 2

try {
// your code
} catch(MidiUnavailableException e) {

}


Will make your code more readable with consistent formatting style.

Hope it helps.

[Brian Legg]

I think everyone else answered your question. 1 other thing though, when using any resources that pull/send data from a file or stream you open a connection. You should always include a finally {} block after your catch to close these connections otherwise your program could go into a never ending state of waiting for the stream to end. Your code could work 99% of the time, but the one time it doesn't get the connection and it catches the exception unless you have a finally block your program will be stuck in a never ending state.

HTH

[Ravaa Bal]

Thanks Muhammad for that tip, I shall try and put it to good use!

Brian Legg wrote:I think everyone else answered your question. 1 other thing though, when using any resources that pull/send data from a file or stream you open a connection. You should always include a finally {} block after your catch to close these connections otherwise your program could go into a never ending state of waiting for the stream to end. Your code could work 99% of the time, but the one time it doesn't get the connection and it catches the exception unless you have a finally block your program will be stuck in a never ending state.

HTH

Thanks Brian, do you mean after the last catch block I include another {} block with close() methods? I don't quite understand.

[Brian Legg]

Anytime you open a file or stream (etc) you put it in a try catch block, after any place you do this you should include a finally block to close the resource. If you are doing this in multiple places then you will need multiple finally clauses. I always include all the code that uses the resource inside the try block that way when I am done using the resource it will be closed for sure even if an exception is thrown. For instance...

try {
FileInputStream stream = new FileInputStream("myfile.txt");
...all code that uses stream goes here...
} catch(FileNotFoundException e) {
e.printStackTrace();
} catch(Exception e) {
e.printStackTrace();
} finally {
stream.close()
}


Hope that helps.

[Campbell Ritchie]

Don't you need the finally inside a try, and don't you need an if (myStream != null) test before closing it?

The 1st is because closing might throw an Exception.

The 2nd is because any Exceptions while opening the Stream might present a null Stream to be closed.

I wrote about that last week here.

[Brian Legg]

Good point Campbell... I should have learned my lesson about coding straight into the browser without an IDE

I don't have Java or a compiler at work so I type out some mistakes sometimes, but I think the key points are captured