paint

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.geom.Line2D;

import javax.swing.JPanel;

public class PanelPaint extends JPanel {
    private static final long serialVersionUID = 1L;

    static PanelPaint panelPaint;

    public PanelPaint() {
        panelPaint = this;

        addMouseListener("PEN");
    }

    private Image image;
    private static Graphics2D g2;

    @Override
    public void paintComponent(Graphics g) {
        if(image == null) {
            image = createImage(getWidth(), getHeight());
            g2 = (Graphics2D)image.getGraphics();

            clear();
        }

        g2.setStroke(strokeSize);
        g.drawImage(image, 0, 0, null);
    }

    public void clear() {
        g2.setPaint(Color.WHITE);
        g2.fillRect(0, 0, getWidth(), getHeight());
        g2.setPaint(Color.BLACK);
    }

    private static int oldX, oldY, currentX, currentY;
    static Point point1, point2;

    static BasicStroke strokeSize = new BasicStroke(1);

    static public void addMouseListener(String type) {
        if(type.equals("PEN")) {
            panelPaint.addMouseListener(new MouseAdapter() {
                @Override
                public void mousePressed(MouseEvent e) {
                    oldX = e.getX();
                    oldY = e.getY();
                }
            });
            panelPaint.addMouseMotionListener(new MouseMotionAdapter() {
                @Override
                public void mouseDragged(MouseEvent e) {
                    currentX = e.getX();
                    currentY = e.getY();

                    strokeSize = new BasicStroke(1);
                    g2.drawLine(oldX, oldY, currentX, currentY);

                    panelPaint.repaint();

                    oldX = currentX;
                    oldY = currentY;
                }
            });
        } else if(type.equals("MARKER")) {
            panelPaint.addMouseListener(new MouseAdapter() {
                @Override
                public void mousePressed(MouseEvent e) {
                    oldX = e.getX();
                    oldY = e.getY();
                }
            });
            panelPaint.addMouseMotionListener(new MouseMotionAdapter() {
                @Override
                public void mouseDragged(MouseEvent e) {
                    currentX = e.getX();
                    currentY = e.getY();

                    strokeSize = new BasicStroke(10);
                    g2.drawLine(oldX, oldY, currentX, currentY);

                    panelPaint.repaint();

                    oldX = currentX;
                    oldY = currentY;
                }
            });
        }
         else if(type.equals("LINE")) {
                panelPaint.addMouseListener(new MouseAdapter() {
                    @Override
                    public void mousePressed(MouseEvent e) {
                        point1 = e.getPoint();
                    }
                });
                panelPaint.addMouseMotionListener(new MouseMotionAdapter() {
                    @Override
                    public void mouseDragged(MouseEvent e) {
                        point2 = e.getPoint();

                        g2.draw(new Line2D.Double(point1, point2));

                        panelPaint.repaint();
                    }
                });
            }
    }

    static public void setColor(Color color) {
        g2.setPaint(color);
    }
}