JApplet drawing shapes

    import java.awt.*;
import java.awt.event.*;

import javax.swing.*;

@SuppressWarnings("serial")
public class ShapeApplet extends JApplet{
    //contains all shapes that created
    private ShapeContainer shapeContaiter = new ShapeContainer();

    //main window panels
    private Panel leftPanel = new Panel();
    private Panel rightPanel = new Panel();
    private Panel buttomPanel = new Panel();

    //the panel inside right panel
    private Panel shapesPanel = new Panel();

    private String [] shapeNames = {"Cicle","Rect","Polygon","Line","Cylinder"};
    private Choice shapeChoice = new Choice();


    //defines the colors to choose from
    JColorChooser colorChooser = new JColorChooser(Color.BLACK);

    //item that will be use for painting
    private Shape shapeToDraw;

    //creating shapesButtons 
    ImageIcon iconCircle = new ImageIcon("circle.png", "Circle");
    JButton buttonCircle = new JButton(iconCircle);

    ImageIcon iconLine = new ImageIcon("line.png","Line");
    JButton buttonLine = new JButton(iconLine);

    ImageIcon iconRect = new ImageIcon("rect.png","Line");
    JButton buttonRect = new JButton(iconRect);

    ImageIcon iconPolygon = new ImageIcon("polygon.png","Line");
    JButton buttonPolygon = new JButton(iconPolygon);

    //creating the other tool buttons
    JButton buttonClear = new JButton("Undo");

    Checkbox checkBoxIsTheShapeFilled = new Checkbox("Filled");
    //defines the new canvas
    PaintingCanvas paintingCanvas = new PaintingCanvas();
    //defines the class for buttons actions
    ButtonAction buttonAction = new ButtonAction();

    //save the shape that selected
    private int currentTool = 4;
    //integers to keep the mouse location
    private int xPoint1, xPoint2 = 0, yPoint1,yPoint2 = 0;

    @Override
    public void init() {
        System.out.println("points" + xPoint1+yPoint2);
        //setting location , size and properties
        Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
        int screenWidth = (int) dim.getWidth();
        int screenHeight = (int) dim.getHeight();
        this.setSize(screenWidth,screenHeight-400); 
        //setting layout
        this.setLayout(new BorderLayout());

        //creating the choices for  shapes
        for(int i = 0 ; i < shapeNames.length ; i++ )
            shapeChoice.add(shapeNames[i]);

        //defines left Panel and right Panel properties
        this.leftPanel.setBackground(Color.LIGHT_GRAY);
        this.leftPanel.setLayout(new GridLayout(5, 0));

        this.rightPanel.setBackground(Color.LIGHT_GRAY);
        this.rightPanel.setLayout(new BorderLayout());

        //adding items to the right panel
        this.rightPanel.add(colorChooser, BorderLayout.NORTH);

        //setting the shapes panel
        this.shapesPanel.setLayout(new GridLayout(3,3));
        this.shapesPanel.add(buttonCircle);
        this.shapesPanel.add(buttonLine);
        this.shapesPanel.add(buttonRect);
        this.shapesPanel.add(buttonPolygon);
        this.shapesPanel.add(checkBoxIsTheShapeFilled);

        //adding the shapes panel to the right Panel
        this.rightPanel.add(shapesPanel, BorderLayout.SOUTH);开发者_开发技巧

        //adding items to the left panel
        this.leftPanel.add(buttonClear);

        //defines the location of each item on the main window
        this.add(leftPanel, BorderLayout.WEST);
        this.add(rightPanel, BorderLayout.EAST);
        this.add(buttomPanel,BorderLayout.SOUTH);
        this.add(paintingCanvas,BorderLayout.CENTER);   

        //setting button actions
        this.buttonCircle.addActionListener(buttonAction);
        this.buttonLine.addActionListener(buttonAction);
        this.buttonPolygon.addActionListener(buttonAction);
        this.buttonRect.addActionListener(buttonAction);
        this.buttonClear.addActionListener(buttonAction);


    }

    @Override
    public void start() {

        super.start();
    }

    @Override
    public void stop() {

        super.stop();
    }

    @Override
    public void destroy() {

        super.destroy();
    }

    public class PaintingCanvas extends Canvas implements MouseListener, MouseMotionListener
    {
        public PaintingCanvas()
        {
            addMouseListener(this);
        }
        @Override
        public void mouseClicked(MouseEvent e) {
        }

        @Override
        public void mouseEntered(MouseEvent e) {

        }

        @Override
        public void mouseExited(MouseEvent e) {

        }

        @Override
        public void mousePressed(MouseEvent e) {

            xPoint1 = e.getX();
            yPoint1 = e.getY();
            xPoint2 = e.getX();
            yPoint2 = e.getY();

        }//end of mousePressed


        @Override
        public void mouseReleased(MouseEvent e) {

            xPoint2 = e.getX();
            yPoint2 = e.getY();



            shapeContaiter.add(shapeToDraw);

            System.out.println("Release");
            repaint();

        }


        @Override
        public void update(Graphics g) {
            paint(g);
        }//end of update

        @Override
        public void paint(Graphics g) {

            switch (currentTool)
            {   
                case 0:
                    //System.out.println("Circle pointsxy: " + xPoint1+","+yPoint1);
                    //System.out.println("Circle pointsx2y2: " + xPoint2+","+yPoint2);
                    shapeToDraw = new Circle(xPoint1 , yPoint1, new Point(xPoint2, yPoint2),colorChooser.getColor() , checkBoxIsTheShapeFilled.getState());
                    //System.out.println( "Circle pointsxy: " + shapeToDraw.getLocation());
                    shapeToDraw.draw(g);    

                    break;
                case 1:
                    shapeToDraw = new Line(xPoint1, yPoint1, new Point(xPoint2,yPoint2), colorChooser.getColor(), checkBoxIsTheShapeFilled.getState());
                    shapeToDraw.draw(g);

                    break;
                case 2:

                    break;
                case 3:
                    shapeToDraw = new Rect(xPoint1, yPoint1, new Point(xPoint2, yPoint2), colorChooser.getColor(), checkBoxIsTheShapeFilled.getState());
                    shapeToDraw.draw(g);

                    break;
                case 4:
                    break;
                default:
            }//end of switch

            System.out.println("Size of shapeContianer: "+shapeContaiter.size());
            System.out.println("pointsxy: " + xPoint1+","+yPoint1);
            System.out.println("pointsx2y2: " + xPoint2+","+yPoint2);


        }//end of paint
        @Override
        public void mouseDragged(MouseEvent e) {


        }
        @Override
        public void mouseMoved(MouseEvent e) {
            // TODO Auto-generated method stub

        }

    }//end of canvas

    public class ButtonAction implements ActionListener
    {

        @Override
        public void actionPerformed(ActionEvent e) {

            if ( e.getSource() == buttonCircle)
                currentTool = 0;
            else if ( e.getSource() == buttonLine)
                currentTool = 1;
            else if ( e.getSource() == buttonPolygon)
                currentTool = 2;
            else if ( e.getSource() == buttonRect)
                currentTool = 3;
            else if (e.getSource() == buttonClear){
                currentTool=4;
                if(shapeContaiter.isEmpty()) JOptionPane.showMessageDialog(buttonClear, "Nothing to delete");
                else {

                    Graphics g = paintingCanvas.getGraphics();

                    shapeContaiter.get(shapeContaiter.size()-1).setColor(Color.WHITE);
                    shapeContaiter.get(shapeContaiter.size()-1).draw(g);
                    shapeContaiter.remove(shapeContaiter.size()-1);

                    System.out.println("Size of shapeContianer: "+shapeContaiter.size());
                }
            }


        }//end of action performed

    }//end of ButtonClicked

}

I'm trying to create an Undo button that will erase the last shape from the shapeContainer array and from the canvas. i can put the finger on the problem but when i am trying to erase on of the shapes it erase the shape that i painted before the current shape.

i created Circle,Rect,Polygon,Line classes that after heavy checking seems to be ok.

1. What is the ShapeContainer class? Instead why don't you just use a Stack http://download.oracle.com/javase/6/docs/api/java/util/Stack.html
2. Why the use of awt Panel and Canvas? I would suggest just using JPanel and JComponents instead.
3. Your Button listener is looking very scary with all the if and else statements. Instead use a separate listener for each button. This will simplify the logic which in turn will prevent bugs in your code and make it easier to make changes. (The Action class in the API might be useful to you in this case).