void add(Watcher w, SelectableChannel ch) {
if(watching.containsKey(w) || paused.containsKey(w) || timeheap.contains(w))
throw(new IllegalStateException(w + ": already registered"));
void add(Watcher w, SelectableChannel ch) {
if(watching.containsKey(w) || paused.containsKey(w) || timeheap.contains(w))
throw(new IllegalStateException(w + ": already registered"));