poi对excel单元格的读写操作

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;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;

import static javafx.scene.input.KeyCode.O;

/**
 * @ClassName 类名：ExcelDemo8
 * @Author作者: hzh
 * @Date时间：2018/12/4 15:33
 * 单元格的读写操作
 **/
public class ExcelDemo8 {

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

        InputStream inputStream = new FileInputStream("D://file//font.xls");
        POIFSFileSystem poifsFileSystem = new POIFSFileSystem(inputStream);

        Workbook wb = new HSSFWorkbook(poifsFileSystem);

        Sheet sheet = wb.getSheetAt(0);
        Row row = sheet.getRow(0);
        Cell cell = row.getCell(0);
        if(cell == null){
            row.createCell(4).setCellValue("hi 我被写入了");
        }

        FileOutputStream fileOutputStream = new FileOutputStream("D://file//font.xls");
        wb.write(fileOutputStream);
        wb.close();

    }
}