public NavigableMap<K, V> headMap(K toExclusive) {return subMap(null, NO_BOUND, toExclusive, EXCLUSIVE);}
public java.util.NavigableMap<K, V> headMap(K toExclusive){return this.subMap(default(K), java.util.TreeMap.Bound.NO_BOUND, toExclusive, java.util.TreeMap.Bound.EXCLUSIVE);}