public class MainWindowEngineeringTool extends JFrame implements ActionListener,ChangeListener,
WindowListener, MouseListener
{
// lot of button and panel definitions here
private JPanel mDrawingPnl = new JPanel(); // panel that the drawings will be in it.

pubic static void main(String[] args)
{
JFrame frame = new JFrame();
frame.setTitle("PLS HELP :)");
//setBounds...
//AlwaysOnTop
//resizable = false
frame.setDefaultCloseOperation(WindowConstraints.EXIT_ON_CLOSE);
JComponent panel = new MainWindowEngineeringTool().BuildPanel();
frame.getContentPane().add(panel);
frame.setVisible(true);
}

public MainWindowEngineeringTool() //CONST
{
super();
//some JGoodies related layout definitions
//all Listener implementations to the buttons.
//label and button initializations.

mDrawingPnl.addMouseListener(this);
mDrawingPnl.addMouseMotionListener(this);
mDrawingPnl.setDoubleBuffered(true);
}

public void stateChanged(ChangeEvent e) // Used for color selection
{
if(e.getSource() == mSelectedColor)
{
ColorSelectionModel model = (ColorSelectionModel)e.getSource();
mCurrentColor = model.getSelectedColor();
}
}

public void actionPerformed(ActionEvent e)
{
int returned = this.switchButton(e); // Just used for switch case below, to define what button is clicked.

switch(returned) // just some of the button actions
{
case 8: setShape(CIRCLE); //int parametered shape definer.
break;
case 10: setShape(ARROW);
break;
case 17: mColorDialog.setContentPane(mColorChooser);
mColorDialog.setTitle("Colors");
//setBounds
//setResizable false
//always on top
//visible true
break;
default: break;
}
}

public void setShape(shape_) {shape = shape_;}

public void paint(Graphics g)
{
//g.setColor(mCurrentColor); //throws exception here so İ commented it.
switch(shape)
{
case NONE: g.fillOval(prevX, prevY, 2,2); //simple brushing right?
break;
case CIRCLE: g.drawOval(prevX, prevY, lastX-prevX, lastY-prevY);
break;
//and the other shapes...
default: break;
}
}

public void mousePressed(MouseEvent e)
{
prevX=e.getX();
prevY=e.getY();
}

public void mouseDragged(MouseEvent e)
{
//some code for printing the mouse X and Y positions in the label.
lastX = e.getX();
lastY = e.getY();
prevX = lastX;
prevY = lastY;
}
}