Javaでファイルサイズを取得する方法

https://github.com/aipocom/aipo/blob/master/lib/storage/src/main/java/com/aimluck/eip/services/storage/impl/ALDefaultStorageHandler.java#L395

  protected int getFileSize(File file) {
    if (file == null) {
      return -1;
    }

    FileInputStream fileInputStream = null;
    int size = -1;
    try {
      fileInputStream = new FileInputStream(file);
      BufferedInputStream input = new BufferedInputStream(fileInputStream);
      ByteArrayOutputStream output = new ByteArrayOutputStream();
      byte[] b = new byte[512];
      int len = -1;
      while ((len = input.read(b)) != -1) {
        output.write(b, 0, len);
        output.flush();
      }
      input.close();
      fileInputStream.close();

      byte[] fileArray = output.toByteArray();
      size = fileArray.length;
      output.close();
    } catch (FileNotFoundException e) {
      return -1;
    } catch (IOException ioe) {
      return -1;
    }
    return size;
  }