我如何使用Apache POI在Excel中增加行

Question

I am writing a program to keep track of employee seating using java and apache poi to write to a excel sheet. The program will prompt the user to enter the desk number, employee name(s), and the number of employees sitting at that desk. My problem is that the program only writes the last information that was entered by the user, erasing what was previously entered in that row. How can I keep what was entered in the first row of the excel sheet? I have it set on a loop where the user will keep being prompted for the seating information until the user enters EXIT. I want it to increment down a row every time new information is entered.

This is what I have so far:

import java.util.*;
import org.apache.poi.hssf.usermodel.*;
import org.apache.poi.hssf.util.*; 
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.ss.util.*;
import java.io.*;

public class EmployeeSeatingRep {

public static void main(String[] args){

    String deskNumber = "";
    String employeeName = "";
    int empsAtDesk = 0;
    boolean keepRunning = true;


//Blank workbook
    HSSFWorkbook workbook = new HSSFWorkbook();
//Blank sheet
    HSSFSheet sheet = workbook.createSheet("Seating Details");

//create heading

        Row rowHeading = sheet.createRow(0);
        rowHeading.createCell(0).setCellValue("Desk:");
        rowHeading.createCell(1).setCellValue("Employee(s)Name:");
        rowHeading.createCell(2).setCellValue("Number At Desk:");

//Font size and style loop for my headers

        for(int i = 0; i < 3; i++)
        {
            CellStyle stylerowHeading = workbook.createCellStyle();
            Font font = workbook.createFont();
            font.setBold(true);
            font.setFontName(HSSFFont.FONT_ARIAL);
            font.setFontHeightInPoints((short) 11);
            stylerowHeading.setFont(font);
            stylerowHeading.setVerticalAlignment(CellStyle.ALIGN_CENTER);
            rowHeading.getCell(i).setCellStyle(stylerowHeading);
        }
    while(keepRunning){
        Scanner scnr = new Scanner(System.in);

        System.out.print("Enter desk number: ");
        deskNumber = scnr.nextLine();
        if(deskNumber.equals("EXIT"))
        {
            System.out.print("You have ended the program");
            System.exit(0);
        }
        else
        {
            System.out.print("Enter employee name: ");
            employeeName = scnr.nextLine();
            System.out.print("Enter amount of employees at desk: ");
            empsAtDesk = scnr.nextInt();







//This data needs to be written (Object[])
        Map <String, Object[]> data = new TreeMap<String, Object[]>();
        data.put("2", new Object[] {deskNumber, employeeName, empsAtDesk});

//Iterate over data and write to sheet
        Set<String> keyset = data.keySet();
        int rownum = 1;
        for(String Key : keyset)
        {
            Row row = sheet.createRow(rownum++);
            Object [] objArr = data.get(Key);
            int cellnum = 0;
            for(Object obj : objArr)
            {
                Cell cell = row.createCell(cellnum++);
                if(obj instanceof String)
                {
                    cell.setCellValue((String)obj);
                }
                else if(obj instanceof Integer)
                {
                    cell.setCellValue((Integer)obj);
                }
            }
            if(!(deskNumber.equals("EXIT")))
            {
                rownum++;

        }

//Auto size my columns that will be filled out with user input info.            
        for (int i = 0; i < 3; i++)
        {
            sheet.autoSizeColumn(i);
        }
        }
try{

 //save to excel file
        FileOutputStream out = new FileOutputStream(new File("Employee Seating Report.xls"));
        workbook.write(out);
        out.flush();
        out.close();
        System.out.println("Excel Written Succesfully...");
    } catch (FileNotFoundException e) {

        e.printStackTrace();

    } catch (IOException e){

        e.printStackTrace();

    } catch (Exception e) {

        System.out.println(e.getMessage());
    }
  } 
}       
}//pub static void end brace    
}//pub class end brace

Answer 1

The issue you're describing is caused by this:

int rownum = 1; <--
for(String Key : keyset)
{
    Row row = sheet.createRow(rownum++);

You've declared rownum inside your main loop and as a result, it will always be 1.

Rather than creating, populating and writing out your data map every time through the loop, it would simplify things greatly if you use the loop to build a List of row objects, then write them to the file when the user is done.

Answer 2

Every information entered by the user should be added to a new row in excel so you need to create row outside your for loop and only create cells in for loop for entered data. Something like this:

    Scanner scnr = new Scanner(System.in);

    System.out.print("Enter desk number: ");
    deskNumber = scnr.nextLine();
    if(deskNumber.equals("EXIT"))
    {
        System.out.print("You have ended the program");
        System.exit(0);
    }
    else
    {
        System.out.print("Enter employee name: ");
        employeeName = scnr.nextLine();
        System.out.print("Enter amount of employees at desk: ");
        empsAtDesk = scnr.nextInt(); scnr.next();
        Row row = sheet.createRow(rownum++);
        Object [] objArr = new Object[] {deskNumber, employeeName, empsAtDesk};
        int cellnum = 0;
        for(Object obj : objArr)
        {
            Cell cell = row.createCell(cellnum++);
            if(obj instanceof String)
            {
                cell.setCellValue((String)obj);
            }
            else if(obj instanceof Integer)
            {
                cell.setCellValue((Integer)obj);
            }
        }
  }

Hope this helps.