Java Check 工作簿包含特定电子表格或未使用 Apache POI

Question

我正在使用 apache POI 创建一个包含多个电子表格的 Excel 文件。首先，此方法应在检查工作簿是否存在后检查工作簿是否为空。如果为空，则创建新工作表名称“sheet1”；如果没有，请检查此工作簿中名为“sheet1”的所有工作表。如果是，则向工作表添加新行；如果没有，则创建一个工作表名称“sheet1”。下面是我当前的代码，我认为这不是实现我的目标的正确方法：

    File file = new File("Main Data.xlsx");
    // Retrieve the workbook for the main report
    XSSFWorkbook workbook;
    // Check file existence 
    if (file.exists() == false) {
        // Create new file if it does not exist
        workbook = new XSSFWorkbook();
    } else {
        try ( 
            // Make current input to exist file
            InputStream is = new FileInputStream(file)) {
                workbook = new XSSFWorkbook(is);
            }
    }
    XSSFSheet spreadsheet;
    // Check if the workbook is empty or not
    if (workbook.getNumberOfSheets() != 0) {
        for (int i = 0; i < workbook.getNumberOfSheets(); i++) {
           if (workbook.getSheetName(i).equals(" Enc " + deviceLabel.getText() + " Info. ")) {
                spreadsheet = workbook.getSheet(" Enc " + deviceLabel.getText() + " Info. ");
            } else spreadsheet = workbook.createSheet(" Enc " + deviceLabel.getText() + " Info. ");
        }
    }
    else {
        // Create new sheet to the workbook if empty
        spreadsheet = workbook.createSheet(" Enc " + deviceLabel.getText() + " Info. ");
    }

    // Error here (variable spreadsheet may not have been initialized
    spreadsheet.shiftRows(0, spreadsheet.getLastRowNum(), 23);   

我遇到了两个问题。

1. for循环显然是错误的来实现我的目标。有什么方法可以检查一个 if 语句中是否同时存在空电子表格或命名电子表格？

例如

  if ((workbook.getNumberOfSheets() == 0) && !workbook.getSheet("sheet1").exists()) {
    workbook.createSheet("sheet1");
  } else workbook.getSheet("sheet1")

2. 我不断收到错误，表示电子表格未初始化，但如果删除 for 循环，错误就会消失。

Answer 1

我用以下代码解决了我的问题：

    File file = new File("Main Data.xlsx");
    // Retrieve the workbook for the main report
    XSSFWorkbook workbook;
    // Check file existence 
    if (file.exists() == false) {
        // Create new file if it does not exist
        workbook = new XSSFWorkbook();
    } else {
        try ( 
            // Make current input to exist file
            InputStream is = new FileInputStream(file)) {
                workbook = new XSSFWorkbook(is);
            }
    }
    XSSFSheet spreadsheet = workbook.getSheet("sheet1");
    // Check if the workbook is empty or not
    if (workbook.getNumberOfSheets() != 0) {
        for (int i = 0; i < workbook.getNumberOfSheets(); i++) {
           if (workbook.getSheetName(i).equals("sheet1")) {
                spreadsheet = workbook.getSheet("sheet1");
            } else spreadsheet = workbook.createSheet("sheet1");
        }
    }
    else {
        // Create new sheet to the workbook if empty
        spreadsheet = workbook.createSheet("sheet1");
    }

    // Shift rows down if exist
    spreadsheet.shiftRows(0, spreadsheet.getLastRowNum(), 23);