Number
 class in the java.lang package, 
its subclasses, and the 
situations where you would use instantiations of these classes rather than the
primitive number types.
This section also presents the 
PrintStream and 
DecimalFormat
 classes, which provide methods for writing formatted numerical output.
Finally, the 
Math
 class in java.lang is discussed. It contains mathematical functions
to complement the operators built into the language. This class has 
methods for the trigonometric functions, exponential functions, and so forth.