java - Looking for the right collection - bidirectional unique pairs -

java - Looking for the right collection - bidirectional unique pairs -

i need collection in java represents next info structure: if next inputs need store them described below:

a->b //should stored

a->c //should stored

a->b //should not allowed (stored) anymore in collection already

b->a //should not allowed (stored) a->b in collection

c->b //should stored

d->c //should stored

i hope idea.

i tried hashmap<set<string>, set<string>> mutating keysets goes wrong, described here: http://stackoverflow.com/a/2393748/2346207

you utilize java.util defaults also, illustration set of sets:

class="lang-java prettyprint-override">hashset<hashset<string>> h = new hashset<hashset<string>>(); h.add(new hashset<string>(arrays.aslist("a", "b"))); h.add(new hashset<string>(arrays.aslist("b", "a"))); // ignored h.add(new hashset<string>(arrays.aslist("b", "c"))); // ok, new fellow member

a bit wordy in java oneliners, works.

java collections