docs: public ExcelWriter merge(int firstRow, int lastRow, int firstColumn, int lastColumn, Object content, boolean isSetHeaderStyle) {
  		Assert.isFalse(this.isClosed, "ExcelWriter has been closed!");
  
  		final CellStyle style = (isSetHeaderStyle && null != this.styleSet && null != this.styleSet.headCellStyle) ? this.styleSet.headCellStyle : this.styleSet.cellStyle;
  		CellUtil.mergingCells(this.sheet, firstRow, lastRow, firstColumn, lastColumn, style);
  
  		// 设置内容
  		if (null != content) {
  			final Cell cell = getOrCreateCell(firstColumn, firstRow);
  			CellUtil.setCellValue(cell, content, this.styleSet, isSetHeaderStyle);
  		}
  		return this;
  	}