How to reduce the loading time of an Open file using Swing?

Question

I want to open a file without taking any time.When I click on open Button immediately it has been opened.But,In my application It has taken more than two minutes for large files.I try to open a file,It has size 44MB.This file takes more than two minutes time to open.I want to open large size files quickly.Once check my open action code. The below code shows the working example of my Application. Sample code:

public class OpenDemo extends javax.swing.JFrame {
JTextPane textPane;
JScrollPane scrollPane;
int i=0;
JTextField status;
public OpenDemo() {
    initComponents();
    textPane=new JTextPane();
}
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    tp = new javax.swing.JTabbedPane();
    jMenuBar1 = new javax.swing.JMenuBar();
    jMenu1 = new javax.swing.JMenu();
    open = new javax.swing.JMenuItem();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    jMenu1.setText("File");

    open.setText("Open");
    open.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            openActionPerformed(evt);
        }
    });
    jMenu1.add(open);

    jMenuBar1.add(jMenu1);

    setJMenuBar(jMenuBar1);

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addComponent(tp, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, 400, Short.MAX_VALUE)
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addComponent(tp, javax.swing.GroupLayout.DEFAULT_SIZE, 279, Short.MAX_VALUE)
    );

    pack();
}// </editor-fold>                        

private void openActionPerformed(java.awt.event.ActionEvent evt) {                                     
    JFileChooser fileChooser=new JFileChooser();
    int result = fileChooser.showOpenDialog(this);
                    if (result==JFileChooser.APPROVE_OPTION) {
                        File file = fileChooser.getSelectedFile();
                        try {
                            textPane.setPage(file.toURI().toURL());
                        } catch(Exception e) {
                            e.printStackTrace();
                        }
                    }
      scrollPane=new JScrollPane(textPane);
      tp.add(scrollPane);
      textPane.setCaretPosition(0);   
}                                    

public static void main(String args[]) {
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(OpenDemo.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(OpenDemo.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(OpenDemo.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(OpenDemo.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new OpenDemo().setVisible(true);
        }
    });
}

// Variables declaration - do not modify                     
private javax.swing.JMenu jMenu1;
private javax.swing.JMenuBar jMenuBar1;
private javax.swing.JMenuItem open;
private javax.swing.JTabbedPane tp;
// End of variables declaration                   

}

Answer 1

The SwingWorker API outlines a suitable approach. Because of the size, I'd update a TableModel, as shown here, rather than a text component. Lines will begin appearing almost immediately, while the GUI remains responsive. The listening JTable will need to render only visible lines, and you may be able to leverage sorting and filtering.

Answer 2

There is some overhead (progress animation) and some things I would not have done, like a AWT event thread blocking actionPerformed.

Go with your code to https://codereview.stackexchange.com/ because a code review might be useful.

What I saw as optimizable:

Give an initial capacity to the StringBuilder.

... = new StringBuilder(1024*64); // (int)file.length()?

Replace the Scanner with a BufferdReader using readLine(). Ideal would be to check the speed of Files.readAllBytes; whether a progress indication is needed.

String s = new String(Files.readAllBytes(file.toPath()));

---

Second attempt:

First a sanity measure: closing the file.

Then I did less progress animation, which should definitely speed things up. It will no longer show all text in the text pane, only every hundredth line.

        try (BufferedReader br = new BufferedReader(new FileReader(file))) {
            final int PROGRESS_EVERY = 100;
            while ((line = br.readLine()) != null) {
                lineNumber++;
                text.append(line);
                text.append("\n");
                if (linenumber % PROGRESS_EVERY== 0) {
                    ProgressData data = new ProgressData();
                    data.number = lineNumber;
                    data.line = line;
                    publish(data);
                }
            }
            if (linenumber % PROGRESS_EVERY != 0) {
                ProgressData data = new ProgressData();
                data.number = lineNumber;
                data.line = line;
                publish(data);
            }
        }

And then

    private StringBuilder text = new StringBuilder(1024 * 128);

At last:

Change textPane from JTextPane to JTextArea. Considerable gain in speed.