Create a new version of paste:

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package paint;

import javax.swing.*;

import java.awt.event.*;
import java.awt.*;
import java.awt.geom.*;
import java.util.*;

@SuppressWarnings("serial")
/**
 *
 * @author ramytamer
 */
public final class Paint extends JFrame {

    JButton lineBtn, circleBtn, ellipseBtn, rectangleBtn, squareBtn, triangleBtn, colorBtn;

    public JButton getSquareBtn() {
        return squareBtn;
    }

    public void setSquareBtn(JButton squareBtn) {
        this.squareBtn = squareBtn;
    }

    public JButton getLineBtn() {
        return lineBtn;
    }

    public void setLineBtn(JButton lineBtn) {
        this.lineBtn = lineBtn;
    }

    public JButton getCircleBtn() {
        return circleBtn;
    }

    public void setCircleBtn(JButton circleBtn) {
        this.circleBtn = circleBtn;
    }

    public JButton getEllipseBtn() {
        return ellipseBtn;
    }

    public void setEllipseBtn(JButton ellipseBtn) {
        this.ellipseBtn = ellipseBtn;
    }

    public JButton getRectangleBtn() {
        return rectangleBtn;
    }

    public void setRectangleBtn(JButton rectangleBtn) {
        this.rectangleBtn = rectangleBtn;
    }

    public JButton getTriangleBtn() {
        return triangleBtn;
    }

    public void setTriangleBtn(JButton triangleBtn) {
        this.triangleBtn = triangleBtn;
    }

    public JButton getColorBtn() {
        return colorBtn;
    }

    public void setColorBtn(JButton colorBtn) {
        this.colorBtn = colorBtn;
    }

    public Graphics2D getGraphSettings() {
        return graphSettings;
    }

    public void setGraphSettings(Graphics2D graphSettings) {
        this.graphSettings = graphSettings;
    }

    public int getDrawAction() {
        return drawAction;
    }

    public void setDrawAction(int drawAction) {
        this.drawAction = drawAction;
    }

    public Color getColour() {
        return colour;
    }

    public void setColour(Color colour) {
        this.colour = colour;
    }

    Graphics2D graphSettings;

    int drawAction = 1;

    Color colour = Color.BLACK;

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        Paint paint = new Paint();
    }

    public Paint() {

        this.setSize(800, 670);
        this.setResizable(false);
        this.setTitle("The awesome paint program");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel btnPanel = new JPanel();
        JPanel colorBtnPanel = new JPanel();

        Box btnsBox = Box.createVerticalBox();
        Box colorBtnBox = Box.createVerticalBox();

        setLineBtn(addBtn("./src/line.png", 1, false));
        setCircleBtn(addBtn("./src/circle.png", 2, false));
        setEllipseBtn(addBtn("./src/ellipse.png", 3, false));
        setRectangleBtn(addBtn("./src/rectangle.png", 4, false));
        setSquareBtn(addBtn("./src/square.png", 5, false));
        setTriangleBtn(addBtn("./src/triangle.png", 6, false));

        setColorBtn(addBtn("./src/color.png", 7, true));

        btnsBox.add(getLineBtn());
        btnsBox.add(getCircleBtn());
        btnsBox.add(getEllipseBtn());
        btnsBox.add(getRectangleBtn());
        btnsBox.add(getSquareBtn());
        btnsBox.add(getTriangleBtn());
        colorBtnBox.add(getColorBtn());

        btnPanel.add(btnsBox);
        colorBtnPanel.add(colorBtnBox);

        this.add(btnPanel, BorderLayout.WEST);
        this.add(colorBtnPanel, BorderLayout.EAST);
        this.add(new DrawingBoard(), BorderLayout.CENTER);

        this.setVisible(true);
    }

    public JButton addBtn(String path, int dAction, boolean isColor) {
        JButton btn = new JButton();
        Icon btnIcon = new ImageIcon(path);
        btn.setIcon(btnIcon);

        btn.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                if (isColor) {
                    setColour(JColorChooser.showDialog(null, "Pick a Color", Color.BLACK));
                } else {
                    setDrawAction(dAction);
                    System.out.println(getDrawAction());
                }

            }
        });

        return btn;
    }

    private class DrawingBoard extends JComponent {

        ArrayList<Shape> shapes = new ArrayList<>();
        ArrayList<Color> shapeColor = new ArrayList<>();

        Point startPoint, endPoint;

        public Point getStartPoint() {
            return startPoint;
        }

        public void setStartPoint(Point startPoint) {
            this.startPoint = startPoint;
        }

        public Point getEndPoint() {
            return endPoint;
        }

        public void setEndPoint(Point endPoint) {
            this.endPoint = endPoint;
        }

        public DrawingBoard() {
            this.addMouseListener(new MouseAdapter() {

                @Override
                public void mousePressed(MouseEvent e) {
                    // When the mouse is pressed get x & y position

                    setStartPoint(new Point(e.getX(), e.getY()));
                    System.out.println("Setting start & end point: " + e.getX() + "," + e.getY());
                    setEndPoint(getStartPoint());
                    repaint();
                }

                @Override
                public void mouseReleased(MouseEvent e) {

                    // Create a shape using the starting x & y
                    // and finishing x & y positions
                    Shape theShape = null;

                    if (getDrawAction() == 1) {
                        // Line
                        System.out.println("(x1,y1)->(" + getStartPoint().x + "," + getStartPoint().y + ")");
                        System.out.println("(x2,y2)->(" + e.getX() + "," + e.getY() + ")");
                        theShape = drawLine(getStartPoint().x, getStartPoint().y, e.getX(), e.getY());
                    } else if (getDrawAction() == 2) {
                        // Circle
                        // theShape = drawCircle(getStartPoint().x, getEndPoint().y, e.getX(), e.getY());
                    } else if (getDrawAction() == 3) {
                        // Ellipse
                        // theShape = drawEllipse(getStartPoint().x, getEndPoint().y, e.getX(), e.getY());
                    } else if (getDrawAction() == 4) {
                        // Rectangle
                        theShape = drawRectangle(getStartPoint().x, getStartPoint().y, e.getX(), e.getY());
                    } else if (getDrawAction() == 5) {
                        // Square
                        // theShape = drawSquare(getStartPoint().x, getEndPoint().y, e.getX(), e.getY());
                    } else if (getDrawAction() == 6) {
                        // Triangle
                        // theShape = drawTriangle(getStartPoint().x, getEndPoint().y, e.getX(), e.getY());
                    }

                    // Add shapes, fills and colors to there ArrayLists
                    shapes.add(theShape);
                    System.out.println("Adding Shape");
                    System.out.println(theShape);
                    shapeColor.add(getColour());

                    setStartPoint(null);
                    setEndPoint(null);

                    repaint();

                }
            });

            this.addMouseMotionListener(new MouseMotionAdapter() {

                @Override
                public void mouseDragged(MouseEvent e) {
                    // Get the final x & y position after the mouse is dragged
                    setEndPoint(new Point(e.getX(), e.getY()));
                    System.out.println("Setting end point: " + e.getX() + "," + e.getY());
                    repaint();
                }
            });
        }

        private Line2D.Float drawLine(int x1, int y1, int x2, int y2) {
            return new Line2D.Float(x1, y1, x2, y2);
        }

        private Ellipse2D.Float drawEllipse(
                int x1, int y1, int x2, int y2) {
            int x = Math.min(x1, x2);
            int y = Math.min(y1, y2);
            int width = Math.abs(x1 - x2);
            int height = Math.abs(y1 - y2);

            return new Ellipse2D.Float(
                    x, y, width, height);
        }
        
        private Ellipse2D.Float drawCircle(
                int x1, int y1, int x2, int y2) {
            int x = Math.min(x1, x2);
            int y = Math.min(y1, y2);
            int width = Math.abs(x1 - x2);
            int height = width;

            return new Ellipse2D.Float(
                    x, y, width, height);
        }
        
        
        
        private Rectangle2D.Float drawRectangle(int x1, int y1, int x2, int y2) {

            int x = Math.min(x1, x2);
            int y = Math.min(y1, y2);
 
            int width = Math.abs(x1 - x2);
            int height = Math.abs(y1 - y2);

            return new Rectangle2D.Float(x, y, width, height);
        }
        
        private Rectangle2D.Float drawSquare(int x1, int y1, int x2, int y2) {

            int x = Math.min(x1, x2);
            int y = Math.min(y1, y2);
 
            int width = Math.abs(x1 - x2);
            int height = width;

            return new Rectangle2D.Float(x, y, width, height);
        }
        
        
        
        @Override
        public void paint(Graphics graphics) {
            setGraphSettings((Graphics2D) graphics);

            getGraphSettings().setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            getGraphSettings().setStroke(new BasicStroke(4));

            Iterator<Color> colourCounter = shapeColor.iterator();

            for (Shape shape : shapes) {
                // actually i don't know what is 0.40f :D
                getGraphSettings().setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER));

                getGraphSettings().draw(shape);
                getGraphSettings().setPaint(colourCounter.next());
                getGraphSettings().fill(shape);

            }

            Shape theShape = null;

            if (getStartPoint() != null && getEndPoint() != null) {
                // Color.LIGHT_GRAY
//                    getGraphSettings().setPaint(Color.BLUE);

                if (getDrawAction() == 1) {
                    // Line
                    theShape = drawLine(getStartPoint().x, getStartPoint().y, getEndPoint().x, getEndPoint().y);
                } else if (getDrawAction() == 2) {
                    // Circle
                    
                    theShape = drawCircle(getStartPoint().x, getStartPoint().y, getEndPoint().x, getEndPoint().y);
                } else if (getDrawAction() == 3) {
                    // Ellipse
                    theShape = drawEllipse(getStartPoint().x, getStartPoint().y, getEndPoint().x, getEndPoint().y);
                } else if (getDrawAction() == 4) {
                    // Rectangle
                    theShape = drawRectangle(getStartPoint().x, getStartPoint().y, getEndPoint().x, getEndPoint().y);
                } else if (getDrawAction() == 5) {
                    // Square
                    theShape = drawSquare(getStartPoint().x, getStartPoint().y, getEndPoint().x, getEndPoint().y);
                } else if (getDrawAction() == 6) {
                    // Triangle
                    // theShape = new Triangle().draw(startpoint.x,startpoint.y,e.getX(),e.getY());
                }
            }

            if (theShape != null) {
                graphSettings.draw(theShape);
            }

        }
    }

}