public String copyFile(String oldPath) {
  try {
   String str = "";
   File oldfile = new File(oldPath);
   if (oldfile.exists()) { // 文件存在时
    FileReader fr = new FileReader(oldPath); // 读入原文件

    BufferedReader in = new BufferedReader(fr);
    String s = "";
    while ((s = in.readLine()) != null) {
     str += s;
     str += "\n";
    }
    in.close();
    fr.close();
   } else {
    System.out.println("can not find the file");
    return "can not find the file";
   }
   return str;
  } catch (Exception e) {
   System.out.println("复制单个文件操作出错");
   e.printStackTrace();
   return "can not find the file";
  }

 }