Question

java中读取文件 第一行为空 提示空指针异常 怎么解决？

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package poidemo1;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;

/**
*
* @author Administrator
*/
public class PoiDemo5 {
public static void main(String[] args) throws IOException {
InputStream inputStream=new FileInputStream("f:/设置字体.xls");
POIFSFileSystem fSFileSystem=new POIFSFileSystem(inputStream);
Workbook wb=new HSSFWorkbook(fSFileSystem);
Sheet sheet= wb.getSheetAt(0);//获取一个sheet页
Row row=sheet.getRow(0);//获取第一行
Cell cell=row.getCell(0);//获取单元格
if (cell==null) {
cell=row.createCell(3);
}
cell.setCellType(Cell.CELL_TYPE_STRING);
cell.setCellValue("测试单元格");

FileOutputStream fileOutputStream=new FileOutputStream("f:/设置字体.xls");
wb.write(fileOutputStream);
fileOutputStream.close();
}

}

Answer 1

package poidemo1;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;

/**
 *
 * @author Administrator
 */
public class PoiDemo5 {
    public static void main(String[] args) throws IOException {
        InputStream inputStream=new FileInputStream(new File("f:/设置字体.xls"));
        POIFSFileSystem fSFileSystem=new POIFSFileSystem(inputStream);
        Workbook wb=new HSSFWorkbook(fSFileSystem);
        Sheet sheet= wb.getSheetAt(0);//获取一个sheet页
        Row row=sheet.getRow(0);//获取第一行
        Cell cell=row.getCell(0);//获取单元格
        if (cell==null) {
            cell=row.createCell(3);
        }
        cell.setCellType(Cell.CELL_TYPE_STRING);
        cell.setCellValue("测试单元格");
        
        FileOutputStream fileOutputStream=new FileOutputStream(new File("f:/设置字体.xls"));
        wb.write(fileOutputStream);
        fileOutputStream.close();
    }
    
}

Answer 2

亲，这里你要建一个excel啊，命名为：f:/设置字体.xls

而且new FileInputStream(new File("f:/设置字体.xls")
FileInputStream必须放一个文件对象，所以要new file（）；

追答

亲，记得采纳哦