Primitive Types

• Integer - Group which includes byte, short, int, and long, which are for whole-value signed numbers.

• Floating-  This group includes float and double.

• Characters -This group includes char, which represents symbols in a character set, like letters and numbers.

•  Boolean -This group includes boolean which is a special type for representing true/false values.

Integers

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 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 defines the sign of an integer value. 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.

byte

The smallest integer type is byte. This is a signed 8-bit type that has a range from –128 to 127. Variables of type byte are especially useful when you’re working with a stream of data from a network or file. They are also useful when you’re working with raw binary data that may not be directly compatible with Java’s other built-in types.

Byte variables are declared by use of the byte keyword. For example, the following

declares two byte variables called b and c: 

byte b, c;

short

short is a signed 16-bit type. It has a range from –32,768 to 32,767. It is probably the least-used Java type. Here are some examples of short variable declarations:

short s;

short t;

int

The most commonly used integer type is int. It is a signed 32-bit type that has a range

from –2,147,483,648 to 2,147,483,647. In addition to other uses, variables of type int are

commonly employed to control loops and to index arrays. Although you might think that

using a byte or short would be more efficient than using an int in situations in which the

larger range of an int is not needed, this may not be the case. The reason is that when byte

and short values are used in an expression they are promoted to int when the expression is

evaluated. (Type promotion is described later in this chapter.) Therefore, int is often the best

choice when an integer is needed.

long

long is a signed 64-bit type and is useful for those occasions where an int type is not large

enough to hold the desired value. The range of a long is quite large. This makes it useful

when big, whole numbers are needed. For example, here is a program that computes the

number of miles that light will travel in a specified number of days.

FLOATING

The type float specifies a single-precision value that uses 32 bits of storage. Single precision is faster on some processors and takes half as much space as double precision, but will become imprecise when the values are either very large or very small. Variables of type float are useful when you need a fractional component, but don’t require a large degree of precision. For example, float can be useful when representing dollars and cents.

Here are some example float variable declarations:

float hightemp, lowtemp;

double

Double precision, as denoted by the double keyword, uses 64 bits to store a value. Double

precision is actually faster than single precision on some modern processors that have been

optimized for high-speed mathematical calculations. All transcendental math functions, such

as sin( ), cos( ), and sqrt( ), return double values. When you need to maintain accuracy over