import java.util.concurrent.LinkedBlockingQueue;

/**
 * 消息中心.
 */
public class MsgCenter {

    /**
     * 消息结束符，收到此消息，认为执行结束.
     */
    public static final String END_STR = "--end--";

    /**
     * 消息队列，本身是线程安全的.
     */
    private static final LinkedBlockingQueue<String> queue = new LinkedBlockingQueue<String>();

    /**
     * 放入一条消息.
     * 
     * @param msg
     *            消息内容
     */
    public static void putMsg(final String msg) {
        if (msg == null) {
            return;
        }

        try {
            queue.put(msg);
        } catch (InterruptedException e) {
        }
    }

    /**
     * 取一条消息.
     * 
     * @return 消息内容
     */
    public static String takeMsg() {
        try {
            return queue.take();
        } catch (InterruptedException e) {
            return "";
        }
    }

    /**
     * 清空消息.
     */
    public static void clear() {
        queue.clear();
    }

    /**
     * 打开消息对话框.
     */
    public static void showMsgDialog() {

        // 由于MsgDialog里设置为了模态窗口，导致new MsgDialog()后面的代码不会执行（关闭窗口后才会执行），
        // 所以用一个线程来new对话框.
        new Thread(new Runnable() {

            @Override
            public void run() {
                new MsgDialog().setVisible(true);
            }
        }).start();

        // 休眠半秒，确保消息框先弹出来.
        try {
            Thread.sleep(500);
        } catch (InterruptedException e) {
        }
    }

}

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;
import javax.swing.border.EmptyBorder;

/**
 * 从消息中心取得消息并显示的对话框（模态的）.
 * 
 */
public class MsgDialog extends JDialog {

    private static final long serialVersionUID = 4906144699636471579L;

    private final JPanel contentPanel = new JPanel();

    // 显示消息的文本框
    private JTextArea msgArea;

    // 取消息的线程
    private Thread msgThread = null;

    // 是否正在运行
    private boolean isRunning = false;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        try {
            MsgDialog dialog = new MsgDialog();
            dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
            dialog.setVisible(true);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * Create the dialog.
     */
    public MsgDialog() {
        setModalityType(ModalityType.APPLICATION_MODAL);
        setAlwaysOnTop(true);
        setTitle("执行控制台");
        setDefaultCloseOperation(JDialog.DO_NOTHING_ON_CLOSE);
        setResizable(false);
        setSize(450, 300);
        setLocationRelativeTo(null);
        getContentPane().setLayout(new BorderLayout());
        contentPanel.setBorder(new EmptyBorder(5, 5, 5, 5));
        getContentPane().add(contentPanel, BorderLayout.CENTER);
        contentPanel.setLayout(new BorderLayout(0, 0));
        {
            msgArea = new JTextArea();
            msgArea.setEditable(false);
            contentPanel.add(msgArea);
        }
        {
            JLabel lblNewLabel = new JLabel("消息：");
            contentPanel.add(lblNewLabel, BorderLayout.NORTH);
        }
        {
            JPanel buttonPane = new JPanel();
            buttonPane.setLayout(new FlowLayout(FlowLayout.RIGHT));
            getContentPane().add(buttonPane, BorderLayout.SOUTH);
            {
                JButton okButton = new JButton("关闭");
                okButton.addActionListener(new ActionListener() {
                    public void actionPerformed(ActionEvent e) {
                        // 没有结束，不允许关闭
                        if (isRunning) {
                            JOptionPane.showMessageDialog(MsgDialog.this,
                                    "正在执行，不能关闭。");
                            return;
                        }
                        msgThread.interrupt(); // 中断线程.
                        MsgDialog.this.dispose(); // 哈哈，想了半天，这么最简单。
                    }
                });
                okButton.setActionCommand("OK");
                buttonPane.add(okButton);
                getRootPane().setDefaultButton(okButton);
            }
        }

        getMsg();
    }

    /**
     * 取消息.
     */
    private void getMsg() {

        // 开始运行啦~~
        isRunning = true;

        // 自动启动取消息的线程
        msgThread = new Thread(new Runnable() {

            @Override
            public void run() {
                while (true) {
                    try {
                        // 取一条消息，没有则等待
                        final String msg = MsgCenter.takeMsg();

                        // 消息不为空
                        if (msg != null && msg.length() > 0) {

                            // 取到结束符，则结束线程
                            if (msg.equals(MsgCenter.END_STR)) {
                                break;
                            } else {
                                // 传递给文本框显示
                                SwingUtilities.invokeLater(new Runnable() {
                                    public void run() {
                                        msgArea.append(msg + "\n"); // append方法线程安全.
                                    }
                                });
                            }
                        }

                        // 休息一会
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        // 被中断，退出循环
                        break;
                    }
                }
                // 运行结束
                isRunning = false;
            }
        });
        msgThread.start();
    }

}

MsgCenter.clear(); //清空消息
MsgCenter.showMsgDialog(); //打开消息对话框

...做一些事情
MsgCenter.putMsg("什么什么");

...做一些事情
MsgCenter.putMsg("什么什么");

MsgCenter.putMsg("xxx完毕。");
MsgCenter.putMsg(MsgCenter.END_STR);