title: I want to preserve my data during service restart, but my data is not in simple variable name-value or table format. How should I go about this?
body: <p>I want to preserve data during service restart, which uses a arraylist of {arraylist of integers} and some other variables.
  Since it is about 40-60 MB, I don't want it be generated each time the service restarts(it takes a lot of time); I want to generate data once, and maybe copy it for next service restart.
  How can it be done?</p>
  
  <p>Please consider how will I go about putting a data structure similar to multidimensional array(3d or above) into file, before suggesting writing the data in a file; which when done, will likely take significant time to read too.</p>