POI 同一オブジェクトへの複数スレッドからの書き込みについて

  fun writeBookFromMultiThread() {
    val templatePath = "./work/test.xlsx"
    val outputFilePath = "./out/test.xlsx"
    WorkbookFactory.create(FileInputStream(templatePath)).use { book ->
      val sheet1 = book.getSheetAt(0)
      val sheet2 = book.getSheetAt(1)
      val future1 = CompletableFuture.runAsync { writeSheet1(sheet1) }
      val future2 = CompletableFuture.runAsync { writeSheet2(sheet2) }
      CompletableFuture.allOf(future1, future2).join()
      FileOutputStream(outputFilePath).use { book.write(FileOutputStream(outputFilePath)) }
    }
  }