void add(String previous, String newWord, int n) { // "now is the" -> <PrefixEntry"time">
Hashtable hm = maps[n];
nEntries[n]++;
PrefixEntry e = (PrefixEntry) hm.get(previous);
if (e == null) {
e = new PrefixEntry(previous);
hm.put(previous, e);
}
e.add(newWord);
}
