java excel去除空列

### 使用Apache POI移除Excel文件中的空列

当处理Excel文件并希望移除非空数据列时，可以利用Apache POI库来实现这一目标。下面是一个具体的解决方案：

为了检测和删除工作表内的空白列，程序会遍历每一行的数据单元格，并统计每列中非空单元的数量。如果某列内所有单元均为空，则该列被标记为可删除。

import org.apache.poi.ss.usermodel.*;
import java.io.FileInputStream;
import java.util.ArrayList;
import java.util.List;

public class ExcelColumnRemover {

    public static void main(String[] args) throws Exception {
        String filePath = "example.xlsx";
        
        try (FileInputStream fis = new FileInputStream(filePath);
             Workbook workbook = WorkbookFactory.create(fis)) {

            Sheet sheet = workbook.getSheetAt(0); // 获取第一个sheet
            
            List<Integer> columnsToRemove = findEmptyColumns(sheet);

            removeColumns(sheet, columnsToRemove);

            // Save the changes to a new file.
            FileOutputStream out = new FileOutputStream("output.xlsx");
            workbook.write(out);
            out.close();
        }
    }

    private static List<Integer> findEmptyColumns(Sheet sheet) {
        int lastRowNum = sheet.getLastRowNum();
        boolean[] isEmptyCol = new boolean[sheet.getRow(0).getLastCellNum()];

        for (int colIndex = 0; colIndex < isEmptyCol.length; ++colIndex) {
            boolean isCurrentColEmpty = true;
            
            for (int rowIndex = 0; rowIndex <= lastRowNum && isCurrentColEmpty; ++rowIndex) {
                Row row = sheet.getRow(rowIndex);
                
                if (row != null) {
                    Cell cell = row.getCell(colIndex);
                    
                    if (cell != null && !isEmpty(cell)) {
                        isCurrentColEmpty = false;
                    }
                }
            }
            
            isEmptyCol[colIndex] = isCurrentColEmpty;
        }

        List<Integer> result = new ArrayList<>();
        for (int i = 0; i < isEmptyCol.length; ++i) {
            if (isEmptyCol[i]) {
                result.add(i);
            }
        }
        
        return result;
    }

    private static boolean isEmpty(Cell cell) {
        switch (cell.getCellType()) {
            case STRING:
                return "".equals(cell.getStringCellValue().trim());
            default:
                return false;
        }
    }

    private static void removeColumns(Sheet sheet, List<Integer> colsToDelete) {
        for (Row row : sheet) {
            for (Integer colIndex : colsToDelete) {
                if (row.getCell(colIndex) != null) {
                    row.removeCell(row.getCell(colIndex));
                }
            }
        }
    }
}

此代码片段展示了如何读取指定路径下的Excel文档，识别其中完全由空白组成的列，并最终将其从表格结构中剔除[^1]。