Drag and Resize undecorated JFrame

Currently, I am using the following code to drag and move my undecordated JFrames.

private void initialiseGUI(Component component){
    //<editor-fold defaultstate="collapsed" desc="code">
    component.addMouseListener(new MouseAdapter() {
        public void mousePressed(MouseEvent e) {
            posX = e.getX();
            posY = e.getY();
        }
    });

    component.addMouseMotionListener(new MouseAdapter() {
        public void mouseDragged(MouseEvent evt) {
            //sets frame position when mouse dragged            
            Rectangle rectangle = getBounds();
            getGUI().setBounds(evt.getXOnScreen() - posX, evt.getYOnScreen() - posY, rectangle.width, rectangle.height);
        }
    });
    //</editor-fold>
}

What must I write so that the user can resize it like a decorated window, by dragging the side?

You can check out mr Rob Camick's ComponentResizer class. Pretty simple and straight forward to use.

Just instantiate the ComponentResizer and register the frame with something like:

JFrame frame = new JFrame();
ComponentResizer cr = new ComponentResizer();
cr.registerComponent(frame);
cr.setSnapSize(new Dimension(10, 10));
cr.setMaximumSize(new Dimension(...));
cr.setMinimumSize(new Dimension(...));

Here's a complete example of using the class

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.LineBorder;

public class UndecoratedExample {

    private JFrame frame = new JFrame();

    class MainPanel extends JPanel {

        public MainPanel() {
            setBackground(Color.gray);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(400, 400);
        }
    }

    class BorderPanel extends JPanel {

        private JLabel label;
        int pX, pY;

        public BorderPanel() {
            label = new JLabel(" X ");
            label.setOpaque(true);
            label.setBackground(Color.RED);
            label.setForeground(Color.WHITE);

            setBackground(Color.black);
            setLayout(new FlowLayout(FlowLayout.RIGHT));

            add(label);

            label.addMouseListener(new MouseAdapter() {
                public void mouseReleased(MouseEvent e) {
                    System.exit(0);
                }
            });
            addMouseListener(new MouseAdapter() {
                public void mousePressed(MouseEvent me) {
                    // Get x,y and store them
                    pX = me.getX();
                    pY = me.getY();

                }

                 public void mouseDragged(MouseEvent me) {

                    frame.setLocation(frame.getLocation().x + me.getX() - pX,
                            frame.getLocation().y + me.getY() - pY);
                }
            });

            addMouseMotionListener(new MouseMotionAdapter() {
                public void mouseDragged(MouseEvent me) {

                    frame.setLocation(frame.getLocation().x + me.getX() - pX,
                            frame.getLocation().y + me.getY() - pY);
                }
            });
        }
    }

    class OutsidePanel extends JPanel {

        public OutsidePanel() {
            setLayout(new BorderLayout());
            add(new MainPanel(), BorderLayout.CENTER);
            add(new BorderPanel(), BorderLayout.PAGE_START);
            setBorder(new LineBorder(Color.BLACK, 5));
        }
    }

    private void createAnsShowGui() {
        ComponentResizer cr = new ComponentResizer();
        cr.setMinimumSize(new Dimension(300, 300));
        cr.setMaximumSize(new Dimension(800, 600));
        cr.registerComponent(frame);
        cr.setSnapSize(new Dimension(10, 10));
        frame.setUndecorated(true);
        frame.add(new OutsidePanel());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new UndecoratedExample().createAnsShowGui();
            }
        });
    }
}