Method invokes inefficient Number constructor; use static valueOf instead

Method invokes inefficient Number constructor; use static valueOf instead

From FindBugs:
Using new Integer(int) is guaranteed to always result in a new object
whereas Integer.valueOf(int) allows caching of values to be done by the
compiler, class library, or JVM. Using of cached values avoids object
allocation and the code will be faster.
Values between -128 and 127 are guaranteed to have corresponding cached
instances and using valueOf is approximately 3.5 times faster than using
constructor. For values outside the constant range the performance of
both styles is the same.

Signed-off-by: Yann Simon <yann.simon.fr@gmail.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>