Java Cookbook, 5th Edition

Chapter 5. Numbers

5.0 Introduction

Numbers are basic to just about any computation. They’re used for array indices, temperatures, salaries, ratings, and an infinite variety of things. Yet they’re not as simple as they seem. With floating-point numbers, how accurate is accurate? With random numbers, how random is random? With strings that should contain a number, what actually constitutes a number?

Java has eight built-in, or primitive types, seven of which can be used to represent numbers, summarized in Table 5-1 with their wrapper (object) types, as well as two numeric classes that do not represent primitive types. The eighth primitive, boolean and its wrapper Boolean, aren’t numeric and can’t be treated as such. Note that unlike languages such as C or Perl, which don’t specify the size or precision of numeric types, Java—with its goal of portability—specifies these exactly and states that they are the same on all platforms.

Table 5-1. Numeric types

Built-in type	Object wrapper	Size of built-in (bits)	Contents
byte	Byte	8	Signed integer
short	Short	16	Signed integer
int	Integer	32	Signed integer
long	Long	64	Signed integer
float	Float	32	IEEE-754 floating point (single precision)
double	Double	64	IEEE-754 floating point (double precision)
char	Character	16	Unsigned Unicode character
n/a	BigInteger	unlimited	Arbitrary-size immutable integer value
n/a	BigDecimal	unlimited	Arbitrary-size-and-precision immutable floating-point value

As you can see, Java ...