Question

I am using swing worker to validate files,
I want the startLine and endLine to be sent to the validate class as i do not want to validate the whole file every time. For the first time when an existing file is openend, i want to send the startLine as 0 and endLine as endLine = editorTextArea.getLineCount() – 1;. After that i should be able to send the startLine and endLine to my convenience every second. How do i achieve this?

Validate class:

  class Validate implements Runnable {

     private JTextArea editorTextArea;
     private JTextArea errorTextArea;
     private int startLine;
     private int endLine;

     public Validate(JTextArea editor, JTextArea error, startLine, endLine) {
         this.editorTextArea = editor;
         this.errorTextArea  = error;
         this.startLine = startLine;
         this.endLine = endLine;        
    }

@Override
public void run() {
    SwingWorker worker = new SwingWorker<Void, Void>() {
        @Override
        protected Void doInBackground() throws Exception {
            //CODE TO VALIDATE
            return null;
        }

        @Override
        protected void done() {                
            //CODE TO DISPLAY THE RESULT
        }
    };
    worker.execute();
    }
 }

Main class:

  //Calls the validate
   public void taskExecutor() {               
          ScheduledExecutorService scheduler =
                 Executors.newSingleThreadScheduledExecutor();
           final ScheduledFuture<?> timeHandle =
                 scheduler.scheduleAtFixedRate(new Validate(editorTextArea,   errorTextArea), 0, 1, SECONDS);                 
}


    private void openFileActionPerformed(java.awt.event.ActionEvent evt)      {                                      

  fileChooser.setCurrentDirectory(new File(".txt"));
int result = fileChooser.showOpenDialog(new JPanel());
int totLines = 0;
String[] content = null;

if (result == JFileChooser.APPROVE_OPTION) {
    try {
        filename = String.valueOf(fileChooser.getSelectedFile());
        setTitle(filename);

        FileReader fr = new FileReader(filename);
        editorTextArea.read(fr, null);
        fr.close();
        startLine = 0;
        endLine = editorTextArea.getLineCount() - 1;
        //here i want to call the validate class once. that is askExecutor();                
    } catch (IOException ex) {
        System.out.println(ex);
    }
}
}

Answer 1

A SwingWorker uses an ExecutorService internally, but the worker “is only designed to be executed once.” I don’t see why you’re wrapping the worker in a Runnable that’s scheduled at a fixed rate. Instead, execute() the task once and let it publish() interim results that can be process()ed on the EDT. For line numbers, SwingWorker<Boolean, Integer> may be appropriate. Integer would represent the last line number processed, while Boolean would represent the final validation result returned by doInBackground().

If the user is aynchronously selecting multiple files for validation, consider adding each executing worker to a suitable TableModel and displaying the results in the corresponding JTable. @mKorbel has shown several examples featuring JProgressBar.

Addendum: If you’re validating additions to the JTextArea, you’ll want to execute() a new worker each time, passing the new range of line numbers as parameters to the worker’s constructor. This example, which passes a single int count, may suggest the approach. The trigger can be a java.util.Timer, a javax.swing.Timer or even the ScheduledExecutorService you originally proposed.