example8_5.java.bak

不错的教程 适合中高级人员的使用

import java.awt.event.*;import java.awt.*;
import javax.swing.JOptionPane;
class Dwindow extends Frame implements ActionListener
{  TextField inputNumber;
   TextArea  show;
   Dwindow(String s)
   {  super(s);
      inputNumber=new TextField(22); inputNumber.addActionListener(this);
      show=new TextArea(); 
      add(inputNumber,BorderLayout.NORTH); add(show,BorderLayout.CENTER); 
      setBounds(60,60,300,300); setVisible(true);
      validate();
      addWindowListener(new WindowAdapter()
                      {   public void windowClosing(WindowEvent e)
                           { System.exit(0);
                           }
                      }
                   );
   }
   public void actionPerformed(ActionEvent e) 
   {  boolean boo=false;
      if(e.getSource()==inputNumber)
        {  String s=inputNumber.getText();
           char a[]=s.toCharArray();
           for(int i=0;i<a.length;i++)
              {  if(!(Character.isDigit(a[i])))
                      boo=true;         
              } 
           if(boo==true)   //弹出"警告"消息对话框。
              {  JOptionPane.showMessageDialog(this,"您输入了非法字符","警告对话框",
                                             JOptionPane.WARNING_MESSAGE);
                 inputNumber.setText(null); 
              }  
           else if(boo==false)
              {  int number=Integer.parseInt(s);
                 show.append("\n"+number+"平方:"+(number*number));
              }
        }
   }
}
public class Example8_4
{  public static void main(String args[]) 
   {  new Dwindow("带对话框的窗口");
   }
}