Javadoc
Each node stores a character (splitchar) which is part of
some key(s). In a compressed branch (one that only contain
a single string key) the trailer of the key which is not
already in nodes is stored externally in the kv array.
As items are inserted, key substrings decrease.
Some substrings may completely disappear when the whole
branch is totally decompressed.
The tree is traversed to find the key substrings actually
used. In addition, duplicate substrings are removed using
a map (implemented with a TernaryTree!).