thanks a lot! f.

the integers can have 20 different values, 0 to 19. during "training", the program should go through every 3-integer-sequence. first it looks at the first integer of the sequence. if there is no key for that in the first level hasmap yet, it should create a new key+entry pair, with (a string representation of) that integer as key and a new hashmap as the related entry. if there is a key already there, it should pull out the entry for that, which would be a hashmap on "level two". now it should take the second integer from the sequence and look in the second level hash if there is a key already there, etc. basically this leads to a tree structure. 

thing is, i don't know in advance how many HM i will need, because i don't know if every combination of 3-integer-sequence will actually appear. i only know that for 20 possible integer values, 3rd order markov, i will have a maximum number of 421 hashmaps (1 on 1st level, 20 on 2nd level, 400 on 3rd level). but to be able to make a hashmap, i need a name for it (" HashMap hm = new HashMap();"), and it's not possible to prepare the names if i don't know how many HM i will need.

so would it be better to create an array of 421 hashmaps right in the beginning? or have an array of HM and each time i need a new hashmap, expand() it by one?