code: public static File [] getFilesWithPrefix(File dir, final String prefix) {
          FileFilter prefixFilter = new FileFilter() {
                  public boolean accept(File pathname)
                  {
                      return pathname.getName().toLowerCase().
                          startsWith(prefix.toLowerCase());
                  }
              };
          return dir.listFiles(prefixFilter);
      }
docs: Get a list of all files in directory that have passed prefix.
  
  @param dir Dir to look in.
  @param prefix Basename of files to look for. Compare is case insensitive.
  
  @return List of files in dir that start w/ passed basename.