import java.io.*;
import java.util.*;
 public class NewChose 
{

  public static void main(String[] args) 
  {   
      static ArrayList al=new ArrayList();
    File f=new File("c:\\temp\\ch21");
    NewChose.vistAllDirsAndFiles(f);
    public static void visitAllDirsAndFiles(File dir)
      {
      
      for(dir.isDirectory())
      {
        String[] children=dir.list();
        int len=children.length();
        for(int i=0;i<len;i++)
        {
          visitAllDirsAndFiles(new File(dir, children[i]));
        }
      }
      else
      {
        String name=dir.getName();
        String sub=name.substring(name.length()-3,name.length());
        if(sub.equals("txt"))
        {
          al.add(dir);
        }
      }
      }  
    System.out.println(al.toString());
    
  }
}