Java中合并Excel单元格的方法

在Java中操作Excel合并单元格,常用的库有Apache POI和EasyExcel，以下是使用这两种方法合并单元格的示例：

使用Apache POI合并单元格

Apache POI是Java操作Excel最常用的库之一。

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import java.io.FileOutputStream;
import java.io.IOException;
public class MergeCellsExample {
    public static void main(String[] args) throws IOException {
        // 创建新的工作簿
        Workbook workbook = new XSSFWorkbook();
        // 创建工作表
        Sheet sheet = workbook.createSheet("合并单元格示例");
        // 创建行和单元格
        Row row = sheet.createRow(0);
        Cell cell = row.createCell(0);
        cell.setCellValue("合并的单元格");
        // 合并单元格 (起始行, 结束行, 起始列, 结束列)
        sheet.addMergedRegion(new CellRangeAddress(0, 2, 0, 2)); // 合并第1-3行，第1-3列
        // 写入文件
        try (FileOutputStream fileOut = new FileOutputStream("merged_cells.xlsx")) {
            workbook.write(fileOut);
        }
        // 关闭工作簿
        workbook.close();
        System.out.println("Excel文件已创建，单元格已合并");
    }
}

使用EasyExcel合并单元格

EasyExcel是阿里巴巴开源的Excel处理库,性能更好，内存占用更小。

import com.alibaba.excel.EasyExcel;
import com.alibaba.excel.write.metadata.WriteSheet;
import com.alibaba.excel.write.metadata.WriteTable;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
import com.alibaba.excel.write.metadata.holder.WriteTableHolder;
import com.alibaba.excel.write.metadata.style.WriteCellStyle;
import com.alibaba.excel.write.metadata.style.WriteFont;
import com.alibaba.excel.write.style.HorizontalCellStyleStrategy;
import org.apache.poi.ss.usermodel.*;
import java.io.FileOutputStream;
import java.io.IOException;
public class EasyExcelMergeExample {
    public static void main(String[] args) throws IOException {
        // 创建Excel写入器
        String fileName = "easyexcel_merged_cells.xlsx";
        // 创建样式策略
        WriteCellStyle headWriteCellStyle = new WriteCellStyle();
        WriteFont headWriteFont = new WriteFont();
        headWriteFont.setFontHeightInPoints((short) 10);
        headWriteCellStyle.setWriteFont(headWriteFont);
        WriteCellStyle contentWriteCellStyle = new WriteCellStyle();
        WriteFont contentWriteFont = new WriteFont();
        contentWriteFont.setFontHeightInPoints((short) 10);
        contentWriteCellStyle.setWriteFont(contentWriteFont);
        HorizontalCellStyleStrategy horizontalCellStyleStrategy = 
            new HorizontalCellStyleStrategy(headWriteCellStyle, contentWriteCellStyle);
        // 构建写入器
        EasyExcel.write(fileName)
            .registerWriteHandler(horizontalCellStyleStrategy)
            .registerWriteHandler(new CustomMergeStrategy())
            .sheet("合并单元格示例")
            .doWrite(() -> {
                // 这里可以添加数据，但合并操作由CustomMergeHandler处理
                return null;
            });
        System.out.println("EasyExcel文件已创建，单元格已合并");
    }
    // 自定义合并策略
    public static class CustomMergeStrategy implements WriteHandler {
        @Override
        public void sheetCreateBefore(WriteSheetHolder writeSheetHolder) {
        }
        @Override
        public void sheetCreateAfter(WriteSheetHolder writeSheetHolder) {
        }
        @Override
        public void rowCreateBefore(WriteSheetHolder writeSheetHolder, WriteTableHolder writeTableHolder, Row row, Head head, Integer relativeRowIndex, Boolean isHead) {
        }
        @Override
        public void rowCreateAfter(WriteSheetHolder writeSheetHolder, WriteTableHolder writeTableHolder, Row row, Head head, Integer relativeRowIndex, Boolean isHead) {
        }
        @Override
        public void cellCreateBefore(WriteSheetHolder writeSheetHolder, WriteTableHolder writeTableHolder, Cell cell, Head head, Integer relativeRowIndex, Boolean isHead, Integer relativeCellIndex) {
        }
        @Override
        public void cellCreateAfter(WriteSheetHolder writeSheetHolder, WriteTableHolder writeTableHolder, Cell cell, Head head, Integer relativeRowIndex, Boolean isHead, Integer relativeCellIndex) {
            // 在这里实现合并逻辑
            if (relativeRowIndex == 0) { // 假设第一行需要合并
                sheet.addMergedRegion(new CellRangeAddress(0, 2, 0, 2));
            }
        }
    }
}

注意事项

1. 合并范围：合并区域必须是连续的矩形区域，不能是分散的单元格。
2. 数据覆盖：合并后，只有左上角的单元格有数据，其他单元格的数据会被忽略。
3. 样式继承：合并后的单元格会继承左上角单元格的样式。
4. 性能考虑：对于大型Excel文件，EasyExcel通常比Apache POI更高效。

更复杂的合并场景

如果需要根据数据动态合并单元格（例如合并相同值的单元格），可以实现更复杂的逻辑：

// Apache POI示例 - 合并相同值的单元格
public void mergeCellsByValue(Sheet sheet, int columnIndex) {
    int firstRow = 0;
    String prevValue = "";
    for (int i = 0; i <= sheet.getLastRowNum(); i++) {
        Row row = sheet.getRow(i);
        if (row == null) continue;
        Cell cell = row.getCell(columnIndex);
        String currentValue = getCellValueAsString(cell);
        if (currentValue.equals(prevValue)) {
            // 合并相同值的单元格
            sheet.addMergedRegion(new CellRangeAddress(firstRow, i - 1, columnIndex, columnIndex));
        }
        prevValue = currentValue;
        firstRow = i;
    }
}
private String getCellValueAsString(Cell cell) {
    if (cell == null) return "";
    switch (cell.getCellType()) {
        case STRING:
            return cell.getStringCellValue();
        case NUMERIC:
            return String.valueOf(cell.getNumericCellValue());
        case BOOLEAN:
            return String.valueOf(cell.getBooleanCellValue());
        case FORMULA:
            return cell.getCellFormula();
        default:
            return "";
    }
}

代码可以根据实际需求进行调整和扩展。