title: How to build an hierarchy tree of categories in java using enums or any other way?
body: <p>Assuming that we have a set of categories: categories={A,B}. Let's assume more that A consists of subcategories: {A1,A2,A3} and B consists of subcategories: {B1,B2}.In addition, there are even more subcategories as follows: for A1:{A1a,A1b}, for A2:{A2a,A2b}, for A3:{A3a,A3b,A3c}, for B1:{B1a,B1b,B1c}, for B2:{B2a,B2b}. How can I build an hierarchical structure in java? </p>
  
  <p>Since the cardinality of each set is fixed and known in advance, my initial approach is to use enum types instead of building classes with inheritance, but I am open to any suggestion. I do not know how to approach this problem.</p>
  
  <p>Thanks in advance.</p>