Java Program any letter to upper case Letter(JavaSWING) ActionListener

import java.awt.event.*;

import java.awt.*;

import javax.swing.*;

class MyFrame extends JFrame implements ActionListener{

Container c;

JTextField t1;

JButton b1;

MyFrame(){

c=this.getContentPane();

c.setLayout(null);

t1 = new JTextField();

t1.setBounds(100,50,210,50);

c.add(t1);

b1 = new JButton("CLick");

b1.setBounds(100,100,150,40);

c.add(b1);

b1.addActionListener(this);

}

public void actionPerformed(ActionEvent e){

String str =t1.getText();

t1.setText(str.toUpperCase());

}

}

class Uper{

public static void main(String[] args) {

MyFrame f = new MyFrame();

f.setBounds(100,100,800,400);

f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

f.setTitle("to upper case");

f.setVisible(true);

}

}