Graphics Program in Swing

import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

class ass2 extends JFrame

            implements KeyListener, ActionListener, MouseMotionListener, MouseListener

{

            JButton btn1, btn2, btn3, btn4, btn5, btn6;

            JTextField txt1, txt2;

            JLabel lbl;

            JPanel pan1, pan2;

            Graphics g;

            Color c;

            JColorChooser ch;

            int mX1, mY1;

            int mX2, mY2;

            int flag;

            Dimension D;

            int Dh, Dw;

            ass2()

            {

                        g = getGraphics ();

                        D = new Dimension ();

                        c = new Color (0, 0, 250);

                        ch = new JColorChooser();

                        btn1 = new JButton ("Line");

                        btn2 = new JButton ("F Line");

                        btn3 = new JButton ("Rect");

                        btn4 = new JButton ("F Rect");

                        btn5 = new JButton ("Color");

                        btn6 = new JButton ("Clear");

                        btn2.setMnemonic ('L');

                        btn4.setMnemonic ('R');

                        btn5.setMnemonic ('o');

                        txt1=new JTextField (20);

                        txt2=new JTextField (20);

                        txt1.setEnabled (false);

                        txt2.setEnabled (false);

lbl = new JLabel ("Press => l :Line  L :F Line  r :Rect  R :FRect      o :Color   c :Clear");

                        pan1 = new JPanel ();

                        pan2 = new JPanel ();

                        pan1.add (btn1);

                        pan1.add (btn2);

                        pan1.add (btn3);

                        pan1.add (btn4);

                        pan1.add (btn5);

                        pan1.add (btn6);

                        add (pan1, BorderLayout.NORTH);

                        pan2.add (txt1);

                        pan2.add (txt2);

                        add (pan2, BorderLayout.CENTER);

                        add (lbl, BorderLayout.SOUTH);

                        setTitle ("Ass 2");

                        setSize (700, 600);

                        setDefaultCloseOperation (EXIT_ON_CLOSE);

                        setVisible (true);

                        addKeyListener (this );

                        btn1.addActionListener (this );

                        btn2.addActionListener (this );

                        btn3.addActionListener (this );

                        btn4.addActionListener (this );

                        btn5.addActionListener (this );

                        btn6.addActionListener (this );

                        addMouseMotionListener (this );

                        addMouseListener (this );

                        requestFocus ();

            }

            public void myJob ()

            {

                        g.setColor (c);

                        g.setClip (30, 100, Dw-60, Dh-130);

                        g.clearRect (30+1, 100+1, Dw-60-1, Dh-130-1);

                        if (flag==1 )

                                    g.drawLine (50, 150, 250, 350);

                        if (flag==2 )

                                    g.drawLine (mX1,mY1, mX2, mY2);

                        if (flag==3 )

                                    g.drawRect (50, 150, 200, 200);

                        if (flag==4 )

                                    g.drawRect (mX1,mY1, mX2-mX1, mY2-mY1);

                        if (flag==5 )

                        {

                                    c=ch.showDialog (ch, "Color Chooser", c);

                                    flag=1;

                        }

                        if (flag==6 )

                                    g.clearRect (30+1, 100+1, Dw-60-1, Dh-130-1);

            }

            public void keyPressed (KeyEvent e) {}

            public void keyReleased (KeyEvent e) {}

            public void keyTyped (KeyEvent e)

            {

                        g=getGraphics ();

                        if (e.getKeyChar() == 'l' )

                                    flag = 1;

                        if (e.getKeyChar() == 'L' )

                                    flag = 2;

                        if (e.getKeyChar() == 'r' )

                                    flag = 3;

                        if (e.getKeyChar() == 'R' )

                                    flag = 4;

                        if (e.getKeyChar() == 'o' )

                                    flag = 5;

                        if (e.getKeyChar() == 'c' )

                                    flag = 6;

                        txt1.setText ("Flag: "+flag+"  Char: "+e.getKeyChar() );

                        mX1=mX2=mY1=mY2=0;

                        myJob ();

            }

            public void actionPerformed (ActionEvent e)

            {

                        g=getGraphics ();

                        if (e.getSource () == btn1)

                                    flag=1;

                        if (e.getSource () == btn2)

                                    flag=2;

                        if (e.getSource () == btn3)

                                    flag=3;

                        if (e.getSource () == btn4)

                                    flag=4;

                        if (e.getSource () == btn5)

                                    flag=5;

                        if (e.getSource () == btn6)

                                    flag=6;

                        txt1.setText ("Flag: "+flag);

                        mX1=mX2=mY1=mY2=0;

                        myJob ();

                        this.requestFocus ();

            }

            public void mouseMoved (MouseEvent e)

            {

                        g=getGraphics ();

                        D=this.getSize();

                        Dh=(int)D.getHeight();

                        Dw=(int)D.getWidth();

                        g.drawRect (30, 100, Dw-60, Dh-130);

            }

            public void mouseDragged (MouseEvent e)

            {

                        g=getGraphics ();

                        mX2=e.getX();

                        mY2=e.getY();

                        txt2.setText ("X: "+mX2+"    Y: "+mY2);

                        myJob ();

            }

            public void mousePressed (MouseEvent e)

            {

                        mX1=e.getX();

                        mY1=e.getY();

            }

            public void mouseReleased (MouseEvent e)

            {

                        myJob ();

                        mX1=mX2=mY1=mY2=0;           

            }

            public void mouseClicked (MouseEvent e) {}

            public void mouseEntered (MouseEvent e)    {}

            public void mouseExited (MouseEvent e) {}

            public static void main (String args [] )

            {

                        new ass2();

            }

}