問道java作業題,有分!

import java.awt.FlowLayout;

import java.awt.Label;

import java.awt.TextField;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.awt.event.WindowAdapter;

import java.awt.event.WindowEvent;

import java.awt.*;

import javax.swing.JOptionPane;

public class changeNumto extends Frame{

Button b = new Button("Change");

Label l1 = new Label("Decimal");

Label l2 = new Label("binary");

Label l3 = new Label("octal");

Label l4 = new Label("hex");

int binary1,octal1,hex1;

int x, y;

TextField tf1 = new TextField(null, 10);

TextField tf2 = new TextField(null, 10);

TextField tf3 = new TextField(null, 10);

TextField tf4 = new TextField(null, 10);

public changeNumto() {

super("changeNum");

setLayout(new FlowLayout(FlowLayout.LEFT));

add(l1);

add(tf1);

add(l2);

add(tf2);

add(l3);

add(tf3);

add(l4);

add(tf4);

add(b);

pack();

setVisible(true);

addWindowListener(new WindowAdapter() {

public void windowClosing(WindowEvent e) {

System.exit(0);

}

});

b.addActionListener(new ButtonListener());

}

class ButtonListener implements ActionListener {

public void actionPerformed(ActionEvent e) {

if (tf1.getText() != null) {

try {

x = Integer.parseInt(tf1.getText());

tf2.setText("" + Integer.toBinaryString(x));

tf3.setText("" + Integer.toOctalString(x));

tf4.setText("" + Integer.toHexString(x));

} catch (NumberFormatException ex) {

JOptionPane.showMessageDialog(l1, "You input is not a int, please input a int");

}

}

}

}

public static void main(String[] args) {

new changeNumto();

}

}