public void checkEmpty() {
        if (type == null) {
            type = CellDataTypeEnum.EMPTY;
        }
        switch (type) {
            case STRING:
            case DIRECT_STRING:
            case ERROR:
                if (StringUtils.isEmpty(stringValue)) {
                    type = CellDataTypeEnum.EMPTY;
                }
                return;
            case NUMBER:
                if (numberValue == null) {
                    type = CellDataTypeEnum.EMPTY;
                }
                return;
            case BOOLEAN:
                if (booleanValue == null) {
                    type = CellDataTypeEnum.EMPTY;
                }
                return;
            default:
        }
    }
Ensure that the object does not appear null
fastexcel-core/src/main/java/cn/idev/excel/metadata/data/CellData.java