My question is: will file reading everytime hinder the performance of the or memory or jvm? i don't think the cpu would be involved.
Obviously, reading a file will use up memory, I/O bandwidth and CPU time. But so will everything else you might do instead (e.g. caching the file contents), so just by that we can't really advise you.
Amongst the questions
you should be asking yourself are: How often does this page get accessed? If it's just once an hour or so it doesn't seem worth the effort to worry about this. If it gets accessed every few seconds it would be a different story.
Whether caching will help depends on how often the file changes. How often would the page get accessed between changes? If caching only saves a couple of reads between changes, it's probably not worthwhile doing. On the other hand, if you can serve the cached dozens (or even hundreds) of times between changes, it would be a different story.
If you really wanted to worry about object creation, you could cache the date-related strings (year, month, day, formattedMonth, fileAbsolute), since they only change every 24 hours. You could have a background
thread change those automatically at midnight every day. But, again, whether that's worthwhile depends on how often the page is accessed.
From a design point of view, I wouldn't do I/O in a JSP, but use a
servlet or backing bean instead. Scriptlets in JSP are considered bad design anyway.