java poi能多次调用write方法保存数据吗

是的，Java POI可以多次调用write方法来保存数据。每次调用write方法时，它将覆盖先前保存的数据。如果要将数据追加到现有文件中而不是覆盖它，则可以使用append参数。例如，使用以下代码将数据追加到现有文件中：

FileOutputStream fos = new FileOutputStream("data.xlsx", true); // 注意 append 参数为 true
workbook.write(fos);

相关问题

java poi多线程在同一张表中插入数据

在Java POI中，可以使用多线程在同一张表中插入数据。下面是一个示例代码：

import java.io.FileOutputStream;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class MultiThreadedExcelWriter {

    private static final String FILE_NAME = "test.xlsx";
    private static final int NUMBER_OF_THREADS = 10;
    private static final int ROWS_PER_THREAD = 100;

    public static void main(String[] args) throws Exception {
        XSSFWorkbook workbook = new XSSFWorkbook();
        XSSFSheet sheet = workbook.createSheet("Sheet1");

        ExecutorService executorService = Executors.newFixedThreadPool(NUMBER_OF_THREADS);
        for (int i = 0; i < NUMBER_OF_THREADS; i++) {
            final int startIndex = i * ROWS_PER_THREAD;
            executorService.execute(() -> {
                for (int j = startIndex; j < startIndex + ROWS_PER_THREAD; j++) {
                    Row row = sheet.createRow(j);
                    Cell cell1 = row.createCell(0);
                    cell1.setCellValue("Value " + j);
                    Cell cell2 = row.createCell(1);
                    cell2.setCellValue("Thread " + Thread.currentThread().getId());
                }
            });
        }
        executorService.shutdown();
        executorService.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);

        FileOutputStream outputStream = new FileOutputStream(FILE_NAME);
        workbook.write(outputStream);
        workbook.close();
        outputStream.close();
    }
}

这个示例代码会创建一个包含10个线程的线程池，每个线程会插入100行数据到同一个表中。注意要等待所有线程完成后再保存文件。

java使用poi将excel模板写入数据并保存本地的工具类

以下是一个使用POI将Excel模板写入数据并保存本地的工具类示例：

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellType;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.ss.usermodel.WorkbookFactory;

public class ExcelWriter {
    private File file;
    private Workbook workbook;

    public ExcelWriter(String filePath) throws IOException {
        file = new File(filePath);
        workbook = WorkbookFactory.create(new FileInputStream(file));
    }

    public void writeData(String[] sheetNames, Map<String, Object[][]> data) throws IOException {
        for (String sheetName : sheetNames) {
            Sheet sheet = workbook.getSheet(sheetName);
            Object[][] sheetData = data.get(sheetName);
            if (sheetData != null) {
                int rowIndex = 0;
                for (Object[] rowData : sheetData) {
                    Row row = sheet.getRow(rowIndex);
                    if (row == null) {
                        row = sheet.createRow(rowIndex);
                    }
                    int columnIndex = 0;
                    for (Object cellData : rowData) {
                        Cell cell = row.getCell(columnIndex);
                        if (cell == null) {
                            cell = row.createCell(columnIndex);
                        }
                        if (cellData != null) {
                            if (cellData instanceof Number) {
                                cell.setCellValue(((Number) cellData).doubleValue());
                            } else if (cellData instanceof String) {
                                cell.setCellValue((String) cellData);
                            } else if (cellData instanceof Boolean) {
                                cell.setCellValue((Boolean) cellData);
                            } else {
                                cell.setCellValue(cellData.toString());
                            }
                        }
                        columnIndex++;
                    }
                    rowIndex++;
                }
            }
        }
    }

    public void save() throws IOException {
        workbook.write(new FileOutputStream(file));
        workbook.close();
    }

    public static void main(String[] args) throws IOException {
        ExcelWriter writer = new ExcelWriter("template.xlsx");
        Map<String, Object[][]> data = new HashMap<String, Object[][]>();
        data.put("Sheet1", new Object[][] { { "A1", "B1", "C1" }, { "A2", "B2", "C2" } });
        data.put("Sheet2", new Object[][] { { "X1", "Y1", "Z1" }, { "X2", "Y2", "Z2" } });
        writer.writeData(new String[] { "Sheet1", "Sheet2" }, data);
        writer.save();
    }
}

使用示例：

1. 创建Excel文件"template.xlsx"，在Sheet1和Sheet2中分别添加3列数据；
2. 在Java中使用ExcelWriter类读取"template.xlsx"文件；
3. 调用writeData方法向Sheet1和Sheet2中写入新数据；
4. 调用save方法保存更新后的Excel文件。

注意：ExcelWriter类中的写入数据方法是覆盖式写入，即会清空原有数据，再写入新数据。如果需要追加数据，需要修改方法实现。