In the Java programming language there are both raw and wrapper objects to represent numbers. For example, int and Integer, double and Double, etc. If one wanted to add a numeric object to a Collection object, it required using the wrapper object rather than the raw type.
With the introduction of autoboxing in Java 1.5, moving between these types would largely be handled by the compiler, but there is still a distinction.
Just as with null types, Objective-C also requires that you wrap raw types before inserting them into objects or using them in variable argument lists where the type id is expected. To help us with this, cocoa provides NSNumber.
