java8 sum

//这两部分效果相同

    monitorCount = tableNameList.stream().mapToDouble(tableName -> multiSourceMapper.getCountByMonitorTableName((String) tableName, wrapper)).sum();

    for (Object tableName : tableNameList) {

        monitorCount = monitorCount + multiSourceMapper.getCountByMonitorTableName((String) tableName, wrapper);

    }