import java.awt.*;import java.awt.event.*;
import javax.swing.JOptionPane;
public class Example16_3
{
?public static void main(String args[])
?{
??new DWindow("帶消息框的窗口");
?}
};
class DWindow extends Frame implements ActionListener
{
?TextField inputNumber;
?TextArea text;
?DWindow(String s)
?{
??super(s);
??//setLayout(new FlowLayout());
??setResizable(false);
??
??inputNumber=new TextField(20);
??text=new TextArea(10,20);
??inputNumber.addActionListener(this);
??add(inputNumber,BorderLayout.NORTH);
??add(text,BorderLayout.CENTER);
??setBounds(0,0,200,300);//validate();
??setVisible(true);
??addWindowListener(new WindowAdapter()
???{
????public void WindowClosing(WindowEvent e)
????{
?????System.exit(0);
????}
???});
??validate();
?}
?public void actionPerformed(ActionEvent e)
?{
??boolean boo=false;
??if (e.getSource()==inputNumber)
??{
???String s=new String(inputNumber.getText());
???char a[]=s.toCharArray();
???for (int i=0;i<a.length;i++)
???{
????if (!(Character.isDigit(a[i])))
????{
?????boo=true;
????}
???}
???if (boo==true)
???{
????JOptionPane.showMessageDialog(this,"您輸入了非法字符。","警告對話框",JOptionPane.WARNING_MESSAGE);
????inputNumber.setText(null);
???}
???else if(boo=false)
???{
????int number=Integer.parseInt(s);
????text.append("\n"+number+"平方："+(number*number));
???}
??}
?}
};