title: Aws lambda java - Implement simple cache to read a file
body: <p>I have a lambda process in java and it reads a json file with a table everytime is triggered. I'd like to implement a kind of cache to have that file in memory and I wonder how to do something simple. I don't want to use elasticchache or redis.</p>
  
  <p>I read something similar to my approach in javascript declaring a global variable with let but not sure how to do it in java, where it should be declared and how to test it. Any idea or example you can provide me? Thanks</p>