Three reasons that you might use a Number object rather than a primitive:

 

this piece of writing is reprinted from the following URL:

http://download.oracle.com/javase/tutorial/java/data/numberclasses.html

just for the use of self learning.

 

1. As an argument of a method that expects an object (often used when manipulating collections of numbers).

2. To use constants defined by the class, such as MIN_VALUE and MAX_VALUE, that provide the upper and lower bounds of the data type.

3. To use class methods for converting values to and from other primitive types, for converting to and from strings, and for converting between number systems (decimal, octal, hexadecimal, binary).