@SuppressWarnings("unchecked")
  public final TypeV get( long key ) {
    if( key == NO_KEY ) {
      final Object V = _val_1;
      return V == TOMBSTONE ? null : (TypeV)V;
    }
    final Object V = _chm.get_impl(key);
    assert !(V instanceof Prime); // Never return a Prime
    assert V != TOMBSTONE;
    return (TypeV)V;
  }
Returns the value to which the specified key is mapped, or {@code null}
 if this map contains no mapping for the key.
 <p>More formally, if this map contains a mapping from a key {@code k} to
 a value {@code v} such that {@code key==k}, then this method
 returns {@code v}; otherwise it returns {@code null}.  (There can be at
 most one such mapping.)
@throws NullPointerException if the specified key is null
jctools-core/src/main/java/org/jctools/maps/NonBlockingHashMapLong.java