Java一个简单的文件工具集

 class FileUtils
 {
     //文件目录下文件总数目
     public static int fileNumber(File dir)
     {
         int filenumber = 0;
         if(dir.exists())
         {
             for(File file:dir.listFiles())
             {
                 if(file.isDirectory())
                 {
                     filenumber = filenumber+fileNumber(file);
                 }
                 else
                 {
                     filenumber++;
                 }
             }
         }
         return filenumber;
     }

     //判断文件是否为图片
     public static boolean isImage(File imgFilePath)
     {
         try
         {
             FileInputStream imgfis = new FileInputStream(imgFilePath);
             byte []imgbyte = new byte[imgfis.available()];
             if((imgfis.read(imgbyte))!=-1)
             {
                 if(imgbyte[0] == (byte) 'G' && imgbyte[1] == (byte) 'I' && imgbyte[2] == (byte) 'F')
                 {
                     return true;
                 }
                 else if(imgbyte[1] == (byte) 'P' && imgbyte[2] == (byte) 'N' && imgbyte[3] == (byte) 'G')
                 {
                     return true;
                 }
                 else if(imgbyte[6] == (byte) 'J' && imgbyte[7] == (byte) 'F' && imgbyte[8] == (byte) 'I'&& imgbyte[9] == (byte) 'F')
                 {
                     return true;
                 }
                 else
                 {
                     return false;
                 }
             }
         }catch(Exception e)
         {
             System.out.println(e.toString());
             return false;
         }
         return false;
     }

     //返回该目录下所有文件的文件数组
     public static File[] listAllDirectory(File dir)
     {
         if(dir!=null&&dir.exists())
         {
             File []finalfile = new File[fileNumber(dir)];
             int markfile =0;
             int fileln=0;
             File files[] = dir.listFiles();
             for(int i=0;i<files.length;i++)
             {
                 if(files[i].isDirectory())
                 {
                     listAllDirectory(files[i]);
                 }
                 else
                 {
                     finalfile[markfile++]=files[i];
                 }
             }
             return finalfile;
         }
         else
         {
             return null;
         }
     }

     //复制文件（用文件通道）
     public static void copyFile(File oldFileAbsolutePath,File newFilePath)
     {
         File newFileAbsolutePath = new File(newFilePath,oldFileAbsolutePath.getName());
         FileInputStream fi = null;
         FileOutputStream fo = null;
         FileChannel in = null;
         FileChannel out = null;
         try {
             fi = new FileInputStream(oldFileAbsolutePath);
             fo = new FileOutputStream(newFileAbsolutePath);
             in = fi.getChannel();
             out = fo.getChannel();
             in.transferTo(0, in.size(), out);
         } catch (IOException e)
             {
                 e.printStackTrace();
             }
             finally
                 {
                     try
                         {
                             fi.close();
                             in.close();
                             fo.close();
                             out.close();
                         } catch (IOException e)
                             {
                                 e.printStackTrace();
                             }
                 }
     }
 }