Question

我需要读取excel文件，所以我可以按名称引用列索引，我喜欢这样：

package main;

import java.io.FileInputStream;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.poi.hssf.usermodel.HSSFCell;
import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;

public class ReadExcel {

public static void main(String[] args) {

    try {

        InputStream fs = new FileInputStream("/.../ListProducts.xls");
        HSSFWorkbook wb = new HSSFWorkbook(fs);
        HSSFSheet sheet = wb.getSheetAt(0);



        Map<String, Integer> map = new HashMap<String,Integer>(); //Create map
        HSSFRow row = sheet.getRow(0); //Get first row
        //following is boilerplate from the java doc
        short minColIx = row.getFirstCellNum(); //get the first column index for a row
        short maxColIx = row.getLastCellNum(); //get the last column index for a row
        for(short colIx=minColIx; colIx<maxColIx; colIx++) { //loop from first to last index
        HSSFCell cell = row.getCell(colIx); //get the cell
        map.put(cell.getStringCellValue(),cell.getColumnIndex()); //add the cell contents (name of column) and cell index to the map
        }

        List<ReportRow> listOfDataFromReport = new ArrayList<ReportRow>();
        for(int x = 1; x<=sheet.getPhysicalNumberOfRows(); x++){
         ReportRow rr = new ReportRow(); 
         HSSFRow dataRow = sheet.getRow(x); 

         int idxForColumn1 = map.get("Id"); 
         int idxForColumn2 = map.get("Name"); 
         int idxForColumn3 = map.get("Price"); 

         HSSFCell cell1 = dataRow.getCell(idxForColumn1); 
         HSSFCell cell2 = dataRow.getCell(idxForColumn2); 
         HSSFCell cell3 = dataRow.getCell(idxForColumn3);  

         rr.setColumn1(cell1.getStringCellValue()); 
         rr.setColumn2(cell2.getStringCellValue());
         rr.setColumn3(cell3.getStringCellValue());

         listOfDataFromReport.add(rr);

        }

        for(int j = 0; j< listOfDataFromReport.size();j++){
               System.out.println("Column 1 Value: " +   listOfDataFromReport.get(j).getColumn1());
            //etc...    
            }

    } catch (Exception e) {
        System.out.println(e.getMessage());
    }


}

当我运行程序时，我在输出中得到了这个：

null

我已将excel文件放在正确的目的地，并且列名正确。

修改

当我添加e.printStackTrace();时，我明白了：

java.lang.NullPointerException
at main.ReadExcel.main(ReadExcel.java:51)

null

EDIT2

我注意到setColumn1,setColumn2,...方法的变量是double。

我这样做：

rr.setColumn1(cell1.getNumericCellValue()); 
rr.setColumn2(cell2.getNumericCellValue());
rr.setColumn3(cell3.getNumericCellValue());

当我尝试运行程序来读取数据时出现以下错误：

 Exception in thread "main" java.lang.IllegalStateException: Cannot get 
 a NUMERIC value from a STRING cell at 
 org.apache.poi.hssf.usermodel.HSSFCell.typeMismatch(HSSFCell.java:654)
 at org.apache.poi.hssf.usermodel.HSSFCell.getNumericCellValue(HSSFCell.java:679)

Answer 1

我和@ maytham-got有点不同。假设代码中的列名称正确，我认为这可能是问题所在：

for(int x = 1; x<=sheet.getPhysicalNumberOfRows(); x++){

假设物理行数为3，因此它们编号为0, 1, 2并且您正在迭代直到3，因此当您尝试稍后获取该单元格时，它会抛出NullPointerException 1}}，因为没有这样的行。

尝试在前面提到的x < sheet.getPhysicalNumberOfRows();循环中执行for（小于，不小于/等于）。

使用POI从java读取Excel的列值时出错

1 个答案: