code: public V get(Object key) {
          TreeMapEntry<K,V> p = getEntry(key);
          return (p==null ? null : p.value);
      }
docs: 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} compares
  equal to {@code k} according to the map's ordering, then this
  method returns {@code v}; otherwise it returns {@code null}.
  (There can be at most one such mapping.)
  
  <p>A return value of {@code null} does not <em>necessarily</em>
  indicate that the map contains no mapping for the key; it's also
  possible that the map explicitly maps the key to {@code null}.
  The {@link #containsKey containsKey} operation may be used to
  distinguish these two cases.
  
  @throws ClassCastException if the specified key cannot be compared
  with the keys currently in the map
  @throws NullPointerException if the specified key is null
  and this map uses natural ordering, or its comparator
  does not permit null keys