It would be very easy to make system notification pop up like Microsoft outlook in swing.

package com.vsquaresolution.system.nofitifcation;
import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.LinearGradientPaint;
import java.awt.Toolkit;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;

public class NotificationPopup extends JDialog {
  private final LinearGradientPaint lpg;

  public NotificationPopup() {
    setUndecorated(true);
    setSize(300, 50);
    // size of the screen
    final Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();

    // height of the task bar
    final Insets scnMax = Toolkit.getDefaultToolkit().getScreenInsets(getGraphicsConfiguration());
    final int taskBarSize = scnMax.bottom;

    setLocation(screenSize.width - getWidth(), screenSize.height - taskBarSize  - getHeight());

    // background paint
    lpg = new LinearGradientPaint(0, 0, 0, getHeight() / 2, 
 new float[] { 0f, 0.3f, 1f }, new Color[] 
 { new Color(1f, 1f, 1f), new Color(1f, 1f, 1f), 
  new Color(1f, 1f, 1f) });

    // blue background panel
    setContentPane(new BackgroundPanel());
  }

  private class BackgroundPanel extends JPanel {
    public BackgroundPanel() {
      setOpaque(true);
    }

    @Override
    protected void paintComponent(final Graphics g) {
      final Graphics2D g2d = (Graphics2D) g;
      // background
      g2d.setPaint(lpg);
      g2d.fillRect(1, 1, getWidth() - 2, getHeight() - 2);
      g2d.setColor(Color.ORANGE); //border color

      // border
      g2d.drawRect(0, 0, getWidth() - 1, getHeight() - 1);
    }
  }

  public static void main(final String[] args) {

    SwingUtilities.invokeLater(new Runnable() {
      @Override
      public void run() {
        try {
          UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        } catch (final Exception e1) {
          e1.printStackTrace();
        }

        final NotificationPopup f = new NotificationPopup();

        final Container c = f.getContentPane();
        c.setLayout(new GridBagLayout());

        final GridBagConstraints constraints = new GridBagConstraints();
        constraints.gridx = 0;
        constraints.gridy = 0;
        constraints.weightx = 1.0f;
        constraints.weighty = 1.0f;
        constraints.insets = new Insets(5, 5, 5, 5);
        constraints.fill = GridBagConstraints.BOTH;

        final JLabel l = new JLabel("You have got 2 new Messages.");
        l.setOpaque(false);

        c.add(l, constraints);

        constraints.gridx++;
        constraints.weightx = 0f;
        constraints.weighty = 0f;
        constraints.fill = GridBagConstraints.NONE;
        constraints.anchor = GridBagConstraints.NORTH;

//        final JButton b = new JButton(new AbstractAction("x") {
//
//          @Override
//          public void actionPerformed(final ActionEvent e) {
//            f.dispose();
//          }
//        });

//        b.setOpaque(false);
//        b.setMargin(new Insets(1, 4, 1, 4));
//        b.setFocusable(false);
//
//        c.add(b, constraints);

        f.setVisible(true);
      }
    });
  }
}

package com.vsquaresolution.system.nofitifcation;

import java.awt.Container;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
public class TestNotificationPopUp extends javax.swing.JFrame {
    
    public TestNotificationPopUp() {
        initComponents();
        
    }
    
    // //GEN-BEGIN:initComponents
    private void initComponents() {

        jPanel2 = new javax.swing.JPanel();
        jButton5 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("Antenna");

        jPanel2.setBorder(javax.swing.BorderFactory.createTitledBorder(" System "));

        jButton5.setText("Open Notification");
        jButton5.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton5ActionPerformed(evt);
            }
        });

        org.jdesktop.layout.GroupLayout jPanel2Layout = new org.jdesktop.layout.GroupLayout(jPanel2);
        jPanel2.setLayout(jPanel2Layout);
        jPanel2Layout.setHorizontalGroup(
            jPanel2Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(org.jdesktop.layout.GroupLayout.TRAILING, jPanel2Layout.createSequentialGroup()
                .add(182, 182, 182)
                .add(jButton5)
                .add(256, 256, 256))
        );
        jPanel2Layout.setVerticalGroup(
            jPanel2Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(jPanel2Layout.createSequentialGroup()
                .add(28, 28, 28)
                .add(jButton5)
                .addContainerGap(org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );

        org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(jPanel2, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(jPanel2, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(29, Short.MAX_VALUE))
        );

        pack();
    }// //GEN-END:initComponents

    private void jButton5ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton5ActionPerformed

       SwingUtilities.invokeLater(new Runnable() {
          @Override
          public void run() {
            try {
              UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
            } catch (final Exception e1) {
              e1.printStackTrace();
            }

            final NotificationPopup f = new NotificationPopup();

            final Container c = f.getContentPane();
            c.setLayout(new GridBagLayout());

            final GridBagConstraints constraints = new GridBagConstraints();
            constraints.gridx = 0;
            constraints.gridy = 0;
            constraints.weightx = 1.0f;
            constraints.weighty = 1.0f;
            constraints.insets = new Insets(5, 5, 5, 5);
            constraints.fill = GridBagConstraints.BOTH;

            final JLabel l = new JLabel("You have got 2 new Messages.");
            l.setOpaque(false);

            c.add(l, constraints);

            constraints.gridx++;
            constraints.weightx = 0f;
            constraints.weighty = 0f;
            constraints.fill = GridBagConstraints.NONE;
            constraints.anchor = GridBagConstraints.NORTH;

            f.setVisible(true);
          }
        });

    }//GEN-LAST:event_jButton5ActionPerformed
    
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new TestNotificationPopUp().setVisible(true);
            }
        });
    }
    
    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JButton jButton5;
    private javax.swing.JPanel jPanel2;
    // End of variables declaration//GEN-END:variables
    
}