RandomData

import java.awt.BorderLayout;

import java.awt.EventQueue;

import java.awt.Font;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.beans.PropertyChangeEvent;

import java.beans.PropertyChangeListener;

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.util.ArrayList;

import java.util.List;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JPanel;

import javax.swing.JProgressBar;

import javax.swing.JScrollPane;

import javax.swing.JTextArea;

import javax.swing.SwingWorker;

import org.h2.jdbcx.JdbcDataSource;

/**

 * @author John B. Matthews

 */

public class RandomDataDemo {

    private static final String RUN = "Run";

    private static final String CANCEL = "Cancel";

    private static final String QUIT = "Quit";

    private static final JProgressBar progressBar = new JProgressBar();

    private static final JTextArea textArea = new JTextArea(48, 120);

    private static final JButton run = new JButton(CANCEL);

    private static RandomDataTask task;

    public static void main(String[] args) throws Exception {

        EventQueue.invokeLater(new Runnable() {

            @Override

            public void run() {

                init();

            }

        });

    }

    private static void init() {

        JFrame frame = new JFrame("Random Data Demo");

        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        progressBar.setIndeterminate(true);

        frame.add(progressBar, BorderLayout.NORTH);

        textArea.setEditable(false);

        textArea.setFont(new Font("Monospaced", Font.PLAIN, 12));

        frame.add(new JScrollPane(textArea), BorderLayout.CENTER);

        JPanel panel = new JPanel();

        run.addActionListener(new ActionListener() {

            @Override

            public void actionPerformed(ActionEvent e) {

                String cmd = e.getActionCommand();

                if (RUN.equals(cmd)) {

                    task.cancel(true);

                    execTask();

                    run.setText(CANCEL);

                } else {

                    task.cancel(true);

                    run.setText(RUN);

                }

            }

        });

        panel.add(run);

        JButton quit = new JButton(QUIT);

        quit.addActionListener(new ActionListener() {

            @Override

            public void actionPerformed(ActionEvent e) {

                task.cancel(true);

                System.exit(0);

            }

        });

        panel.add(quit);

        frame.add(panel, BorderLayout.SOUTH);

        frame.pack();

        frame.setVisible(true);

        execTask();

    }

    private static void execTask() {

        textArea.replaceRange(null, 0, textArea.getSelectionEnd());

        progressBar.setIndeterminate(false);

        task = new RandomDataTask(2500);

        task.addPropertyChangeListener(new PropertyChangeListener() {

            @Override

            public void propertyChange(PropertyChangeEvent evt) {

                if ("progress".equals(evt.getPropertyName())) {

                    progressBar.setValue((Integer) evt.getNewValue());

                }

            }

        });

        task.execute();

    }

    /**

     * Get pseudo-random numbers from a data source.

     */

    private static class RandomDataTask

        extends SwingWorker<List<Double>, Double> {

        private static final int BLOCK_SIZE = 10;

        private final int count;

        private final List<Double> numbers;

        private int index = 1;

        private Connection conn;

        private PreparedStatement ps;

        private ResultSet rs;

        RandomDataTask(int count) {

            this.count = count;

            this.numbers = new ArrayList<Double>(count);

            JdbcDataSource ds = new JdbcDataSource();

            ds.setURL("jdbc:h2:file:~/src/java/jdbc/test;IFEXISTS=TRUE");

            ds.setUser("sa");

            ds.setPassword("");

            try {

                this.conn = ds.getConnection();

                ps = conn.prepareStatement(

                    "SELECT RAND() FROM SYSTEM_RANGE(1, ?)");

                ps.setInt(1, BLOCK_SIZE);

            } catch (SQLException ex) {

                ex.printStackTrace(System.err);

            }

        }

        @Override

        public List<Double> doInBackground() {

            try {

                for (int i = 0; i < count / BLOCK_SIZE; i++) {

                    rs = ps.executeQuery();

                    while (rs.next() && !isCancelled()) {

                        if (rs.getBoolean(1)) {

                            double number = rs.getDouble(1);

                            numbers.add(number);

                            setProgress(100 * numbers.size() / count);

                            publish(number);

                        }

                    }

                    Thread.sleep(10); // simulate latency

                }

            } catch (SQLException ex) {

                ex.printStackTrace(System.err);

            } catch (InterruptedException ex) {

                Thread.currentThread().interrupt();

            }

            return numbers;

        }

        @Override

        protected void process(List<Double> chunks) {

            StringBuilder strBuilder = new StringBuilder();

            for (double number : chunks) {

                strBuilder.append(String.format("%1$11.8f", number));

                if (index % BLOCK_SIZE == 0) {

                    strBuilder.append('\n');

                }

                index++;

            }

            textArea.append(strBuilder.toString());

        }

        @Override

        protected void done() {

            run.setText(RUN);

        }

    }

}