List<Entity> baseMess = new ArrayList<>();
baseMess= motiveService.getBaseMessage(machine.get(i),preDate,nowDate);
System.out.println("获取Size"+baseMess.size());
baseMess.removeIf(Objects::isNull);
System.out.println("获取Size"+baseMess.size());            

list为null时结果：

list不为null时结果：

baseMess.removeIf(Objects::isNull);

参考1
参考2