Conversion of string program java

Conversion of string java program UPPER lower BOLD ITALIC 

import javax.swing .* ;
import java.awt . * ;
import java.awt.event .* ;

class Convt extends JFrame implements ActionListener
{
       JLabel l1;
       JButton b1,b2,b3,b4;
       JTextField t1,t2,t3,t4,t5;
     Convt( )
  {
         setVisible(true);
         setSize(400,400);
         setTitle("Conversion of Text");

         l1=new JLabel("ENTER   THE   STRING :=");
         b1=new JButton("LOWER");
         b2=new JButton("UPPER");
         b3=new JButton("BOLD");
         b4=new JButton("ITALIC");
         b1.addActionListener(this);
         b2.addActionListener(this);
         b3.addActionListener(this);
         b4.addActionListener(this);

         t1=new JTextField(10);
         t2=new JTextField(10);
         t3=new JTextField(10);
         t4=new JTextField(10);
         t5=new JTextField(10);

     JPanel p1=new JPanel( );
      p1.setLayout(new GridLayout(5,2));
      p1.add(l1);
      p1.add(t1);
      p1.add(b1);
      p1.add(t2);
      p1.add(b2);
      p1.add(t3);
      p1.add(b3);
      p1.add(t4);
      p1.add(b4);
      p1.add(t5);

     Container cn=getContentPane( );
     cn.setLayout(new FlowLayout( ));
     cn.add(p1);
   }
    public void actionPerformed(ActionEvent ae)
    {
             String s=t1.getText( );
            if(ae.getSource( )==b1)
        {
             t2.setText(s.toLowerCase( ));
           }
       else
           if(ae.getSource( )==b2)
           {
                 t3.setText(s.toUpperCase( ));
                }
       else
          if(ae.getSource( )==b3)
          {
                 t4.setFont(new Font("Dialog",Font.BOLD,20));
                 t4.setText(s);
               }

        else
             if(ae.getSource( )==b4)
            {
                   t5.setFont(new Font("Dialog",Font.ITALIC,20));
                   t5.setText(s);
                 }
        }
      public static void main(String args[])
      {
             Convt cv=new Convt( );
             cv.validate( );
           }
    }