I want to generate a unique id for customers in java, the customer id will take 2 alphabets from country Name (i.e. Australia- AU and America- AM), then pick 2 last digits of year (i.e. 2010- 10) finally I want a counter that can provide me number in a series like 0001, 0002,0003… Now the problem is I am not finding a way to save the last number that was assigned to a customer before closing the application, because every time I restart the application it moves back to -0000.