code: public void setCellMerge(final int colIndex, final int rowMerge, final int columnMerge) throws IOException {
          if (rowMerge <= 0 || columnMerge <= 0) return;
          if (rowMerge <= 1 && columnMerge <= 1) return;
  
          this.parent.setCellMerge(this.rowIndex, colIndex, rowMerge, columnMerge);
      }
docs: Set the merging of multiple cells to one cell.
  
  @param colIndex    The column, 0 is the first column
  @param rowMerge    the number of rows to merge
  @param columnMerge the number of cells to merge
  @throws IOException if the cells can't be merged