import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class LinieZiehen2 extends JPanel implements MouseListener, MouseMotionListener {

    private static final long serialVersionUID = 1L;

    private int startX, startY, tempX, tempY;
    
    private Image img = null;
    
    private static final Color BGCOLOR = new Color(170, 100, 100);

    private static final Color FGCOLOR = new Color(10, 200, 10);

    public LinieZiehen2() {
        this.setBackground(BGCOLOR);
        this.addMouseListener(this);
        this.addMouseMotionListener(this);
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        g2.setPaintMode();
        g.drawImage(img, 0, 0, this);
        g2.setColor(FGCOLOR);
        g2.drawLine(startX, startY, tempX, tempY);
    }
    
    public void zeichne(){
        if(img == null){
            img = createImage(this.getWidth(), this.getHeight());
        }
        Graphics2D g2d = (Graphics2D)img.getGraphics();
        this.paint(g2d);
        g2d.dispose();
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.add(new LinieZiehen2());
        frame.setBackground(BGCOLOR);
        frame.setSize(400, 300);
        frame.setTitle("Eine gerade Linie ziehen");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }

    public void mouseClicked(MouseEvent e) {
    }

    public void mouseEntered(MouseEvent e) {
    }

    public void mouseExited(MouseEvent e) {
    }

    public void mousePressed(MouseEvent e) {
        startX = e.getX();
        startY = e.getY();
    }

    public void mouseReleased(MouseEvent e) {
        zeichne();
    }

    public void mouseDragged(MouseEvent e) {
        tempX = e.getX();
        tempY = e.getY();
        this.repaint();
    }

    public void mouseMoved(MouseEvent e) {
    }
}