用Java 多线程写一个读写大文件excel的工具类

好的，我可以为您提供一个Java多线程读写大文件excel的工具类。您可以使用Apache POI库来读写excel文件，同时使用Java多线程来提高读写效率。以下是一个简单的示例代码：

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
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 org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class ExcelReadWriteUtil {

    private static final int THREAD_POOL_SIZE = 10;

    public static void readWriteExcel(File inputFile, File outputFile) throws IOException {
        Workbook workbook = new XSSFWorkbook(new FileInputStream(inputFile));
        Sheet sheet = workbook.getSheetAt(0);
        int rowCount = sheet.getLastRowNum() - sheet.getFirstRowNum();
        ExecutorService executor = Executors.newFixedThreadPool(THREAD_POOL_SIZE);
        for (int i = 1; i <= rowCount; i++) {
            Row row = sheet.getRow(i);
            executor.execute(new ExcelRowProcessor(row, outputFile));
        }
        executor.shutdown();
        while (!executor.isTerminated()) {
            // Wait for all threads to finish
        }
        workbook.close();
    }

    private static class ExcelRowProcessor implements Runnable {

        private final Row row;
        private final File outputFile;

        public ExcelRowProcessor(Row row, File outputFile) {
            this.row = row;
            this.outputFile = outputFile;
        }

        @Override
        public void run() {
            try {
                Workbook workbook = new XSSFWorkbook(new FileInputStream(outputFile));
                Sheet sheet = workbook.getSheetAt(0);
                int rowNum = sheet.getLastRowNum() + 1;
                Row newRow = sheet.createRow(rowNum);
                for (int j = 0; j < row.getLastCellNum(); j++) {
                    Cell cell = newRow.createCell(j);
                    cell.setCellValue(row.getCell(j).getStringCellValue());
                }
                FileOutputStream outputStream = new FileOutputStream(outputFile);
                workbook.write(outputStream);
                workbook.close();
                outputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

您可以将输入文件和输出文件作为参数传递给`readWriteExcel`方法。该方法会使用多线程读取输入文件中的每一行，并将每一行写入输出文件中。每个线程都会创建一个新的工作簿对象，并将每一行写入输出文件中。请注意，此示例代码仅适用于.xlsx格式的Excel文件。如果您需要处理.xls格式的文件，则需要使用HSSFWorkbook而不是XSSFWorkbook。