程序代码：

import java.awt.event.*;

import java.awt.*;

import javax.swing.*;

import java.util.regex.*;

import java.io.*;

public class Exercise {

    public static void main(String args[]){

     new Dwindow();

    }

}

class Dwindow extends JFrame implements ActionListener{

JButton inputNumber;

JTextArea save;

Pattern p;

Matcher m;

File file=new File("data.txt");

Dwindow(){

inputNumber=new JButton("单击按钮打开输入对话框");

inputNumber.addActionListener(this);

save=new JTextArea(12,16);

add(inputNumber,BorderLayout.NORTH);

add(new JScrollPane(save),BorderLayout.CENTER);

p=Pattern.compile("\\D+");

setBounds(60,60,300,300);

setVisible(true);

setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

public void actionPerformed(ActionEvent e)

{

String str=JOptionPane.showInputDialog(null,"请输入数字字符","输入对话框",JOptionPane.INFORMATION_MESSAGE);

if(str!=null){

m=p.matcher(str);

while(m.find()){

JOptionPane.showMessageDialog(this,"你输入了非法字符","消息对话框",JOptionPane.WARNING_MESSAGE);

str=JOptionPane.showInputDialog(null,"请输入数字字符序列");

m=p.matcher(str);

}

if(Integer.parseInt(str)>1000){

     int n=JOptionPane.showConfirmDialog(this,"你输入的数字大于1000，是否继续将数字存入文件？","确认对话框",JOptionPane.YES_NO_CANCEL_OPTION);

     if(n==JOptionPane.YES_OPTION)

    save.append("\n"+str);

}

else

      save.append("\n"+str);

byte b[]=str.getBytes();

try{

FileOutputStream out=new FileOutputStream(file,true);

OutputStreamWriter writer=new OutputStreamWriter(out);

//out.write(b);

//out.close();

writer.write(str+'\0');

writer.close();

out.close();

    }

catch(IOException f){

 System.out.println(f);

    }

}

}

}