Which is better for fresh graduates with poor foundation to learn linux operation and maintenance engineers or java development?

We can't simply regard two directions as good or bad. Let's just say that Linux operation and maintenance still depends on code development, and Java development does not necessarily need to be carried out under Linux. It has nothing to do with the foundation. You basically need to sublimate your early learning ideas after you enter the business, so you need to be careful about your learning attitude. From a professional point of view, Linux operation and maintenance is more promising.