이 컴퓨터 의 모든 접미사 파일 이름 가 져 오기 --- 자바

package com.satan.suffix;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

public class CountSuffix
{
   private static Set<String> suffixSet = new HashSet<String>();
   private static String file = "F:\\1.txt";
   public static void main(String[] args) throws IOException
   {
       long start,end;

       start = System.currentTimeMillis();
       countSuffix(File.listRoots());
       System.out.println("   " + suffixSet.size()+ "    ");
       end = System.currentTimeMillis();
       System.out.println("Time use: " + (end-start) + "ms");
       
       
       FileOutputStream fos = new FileOutputStream(file);
       OutputStreamWriter osr = new OutputStreamWriter(fos);
       BufferedWriter bw = new BufferedWriter(osr);

       Iterator<String> iter = suffixSet.iterator();
       while(iter.hasNext())
       {
           bw.write(iter.next()+"\r
");
       }
       bw.close();
   }
   
   private static void countSuffix(File[] files) throws IOException
   {
       if(files != null)
       {
           for (File file : files)
           {
               if(file != null)
               {
                   if(file.isFile() && file.getName().contains("."))
                   {
                       String fileName = file.getName();
                       String[] word = fileName.split("\\.");//split            
                       suffixSet.add(word[word.length-1]);
                   }
                   countSuffix(file.listFiles());
               }
           }
       }
   }
}