Guava: Set + Function = Map?

Question

Is there an idiomatic way to take a Set and a Function, and get a Map live view? (i.e. the Map

Answer 1

Caution. Sean Patrick Floyd's answer, although very useful, has a flaw. A simple one, but took me a while to debug so don't fall in the same trap: the MapEntry class requires equals and hashcode implementations. Here are mine (simple copy from the javadoc).

@Override
public boolean equals(Object obj) {
    if (!(obj instanceof Entry)) {
        return false;
    }
    Entry e2 = (Entry) obj;
    return (getKey() == null ? e2.getKey() == null : getKey().equals(e2.getKey()))
        && (getValue() == null ? e2.getValue() == null : getValue().equals(e2.getValue()));
}

@Override
public int hashCode() {
    return (getKey() == null ? 0 : getKey().hashCode()) ^
        (getValue() == null ? 0 : getValue().hashCode());
}

This reply would be better as a commentary to the relevant answer, but AFAIU I don't have the right to post a comment (or did't find how to!).