Doubles.constrainToRange(double,double,double) and Floats.constrainToRange(float,float,float) both cause unnecessary boxing of their arguments. Both call Preconditions.checkArgument(boolean, String, **Object**, **Object**) which causes the boxing.

Can be easily fixed by introducing an overloaded version of checkArgument for floats and doubles. For ints and longs these versions already exist:
Preconditions.checkArgument(boolean, String, **int**, **int**)
Preconditions.checkArgument(boolean, String, **long**, **long**)
which is also why constrainToRange does not have the same problem in the Ints, Shorts & Longs packages.
private static final class Values<K, V> extends ImmutableList<V> {
    final RegularImmutableMap<K, V> map;
    Values(RegularImmutableMap<K, V> map) {
      this.map = map;
    }
    @Override
    public V get(int index) {
      return map.entries[index].getValue();
    }
    @Override
    public int size() {
      return map.size();
    }
    @Override
    boolean isPartialView() {
      return true;
    }
  }
  
  
  private static final long serialVersionUID = 0;
}