code: private static String checkPath(String path) {
          File file = new File(path);
          int idx = path.lastIndexOf(".");
          String post = "";
          if (idx > -1) {
              post = path.substring(idx);
              path = path.substring(0, idx);
          }
          int i = 0;
          while (file.exists()) {
              file = new File(path + "_" + (++i) + post);
          }
          return file.getAbsolutePath();
      }
docs: 检查文件路径是否存在
  
  @param path 文件路径
  
  @return 文件的绝对路径，如果文件存在，则生成一个新路径