Java 5 introduced some new static factory methods (called valueOf()) in the Number sub-classes, to be used in preference of the constructors unless a fresh instance is required. The valueOf() methods are allowed to cache and reuse objects, possibly reducing the allocation/gc cost and the memory footprint. For example, Integer.valueOf(int) uses a pre-allocated cache for values between -128 and +127 by default (the cache size can be tuned with JVM flags).
Now that the server and client code is compiled against Java 5 libraries, we should use the valueOf() methods to get those benefits. Note also that Java 5 auto-boxing of numbers uses these methods implicitly, so in many cases we can just remove the calls to the constructor and the compiler will automatically insert the calls for us.