Java defines four integer types: byte, short, int, and long. All of these are signed, positive
and negative values. Java does not support unsigned, positive-only integers. Many other
computer languages, including C/C++, support both signed and unsigned integers.
However, Java’s designers felt that unsigned integers were unnecessary. Specifically,
they felt that the concept of unsigned was used mostly to specify the behavior of the
high-order bit, which defined the sign of an int when expressed as a number. As you will
see in Chapter 4, Java manages the meaning of the high-order bit differently, by adding
a special “unsigned right shift” operator. Thus, the need for an unsigned integer type
was eliminated.
The width of an integer type should not be thought of as the amount of storage it
consumes, but rather as the behavior it defines for variables and expressions of that
type. The Java run-time environment is free to use whatever size it wants, as long as
the types behave as you declared them. In fact, at least one implementation stores bytes
and shorts as 32-bit (rather than 8- and 16-bit) values to improve performance, because
that is the word size of most computers currently in use.
The width and ranges of these integer types vary widely, as shown in this table:
Name Width Range
long 64 –9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
int 32 –2,147,483,648 to 2,147,483,647
short 16 –32,768 to 32,767
byte 8 –128 to 127
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