从你的描述看来 Excel 十进制分隔符是当前区域设置中的逗号。所以这个逗号 {"0,5", "1", "1,5", "2", "2,5"} 与列表约束公式中用作列表分隔符的逗号冲突。这是因为此列表约束公式将 <formula1>"0,5,1,1,5,2,2,5"</formula1> .
使用时 {"0.5", "1", "1.5", "2", "2.5"} ，列表约束公式为 <formula1>"0.5,1,1.5,2,2.5"</formula1> . 但是现在这个公式中的点与您的区域设置冲突，在日期文本中逗号作为十进制分隔符，点作为分隔符。
这是一个众所周知的问题 Excel 问题。当前 Excel 版本通过使用不同类型的存储列表约束来解决此问题： <x12ac:list>"0,5",1,"1,5",2,"2,5"</x12ac:list> 而不是： <formula1>"0,5,1,1,5,2,2,5"</formula1> . 但是 apache poi 不支持此操作。
作为一种解决方法，我建议使用隐藏的工作表来存储列表项。
例子：

import java.io.*;

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.*;

import org.apache.poi.ss.util.*;

class CreateExcelDataValidationListName {

 public static void main(String[] args) throws Exception{

   Workbook workbook = new XSSFWorkbook();  

   //create sheet for storing the list items:
   Sheet sheet = workbook.createSheet("ListSheet");
   sheet.createRow(0).createCell(0).setCellValue("SourceList");
   int r = 1;
   for (double d = 0.5; d < 3; d+=0.5) {
    sheet.createRow(r++).createCell(0).setCellValue(d);
   }
   //unselect that sheet because we will hide it later
   sheet.setSelected(false);
   //create a named range for the list contraint
   Name namedCell = workbook.createName();
   namedCell.setNameName("SourceList");
   String reference = "ListSheet!$A$2:$A$5";
   namedCell.setRefersToFormula(reference);

   //create the visible sheet
   sheet = workbook.createSheet("Sheet1");

   sheet.createRow(0).createCell(0).setCellValue("Take the ListItems from B1:");
   sheet.setActiveCell(new CellAddress("B1"));

   sheet.autoSizeColumn(0);

   //create the data validation
   DataValidationHelper dvHelper = sheet.getDataValidationHelper();
   DataValidationConstraint dvConstraint = dvHelper.createFormulaListConstraint("SourceList");
   CellRangeAddressList addressList = new CellRangeAddressList(0, 0, 1, 1);            
   DataValidation validation = dvHelper.createValidation(dvConstraint, addressList);

   sheet.addValidationData(validation);

   //hide the ListSheet
   workbook.setSheetHidden(0, true);
   //set Sheet1 active
   workbook.setActiveSheet(1);

   FileOutputStream out = new FileOutputStream("CreateExcelDataValidationList.xlsx");
   workbook.write(out);
   out.close();
   workbook.close();

 }
}