Storing and Naming Data - JAVA Programming for Engineers - page 35

circumferenceofacircle.Oncedefined,thisvaluecanberecalledany
timethatitisneeded.

Java variable types
Javaisa stronglytyped language.Thismeansthateveryvariablemusthave
adeclaredtype,andthatthelanguagestrictlyenforcestype-checking.
EightprimitivedatatypesarebuiltintotheJavalanguage.Fourofthese
primitivetypes,calledintegertypes,areusedtostorewholenumbers.They
arenamed byte,short,int ,and long .Twoprimitivetypesareusedforstor-
ingdecimalnumbers.Thesetypesarenamed float and double .Thereisalso
onecharactertype,named char ,andonebooleantype,named boolean . Ta-
ble4-1 liststheJavaprimitivedatatypes.

Table4-1
JavaPrimitiveDataTypes

TYPENAME STORAGE APPROXIMATE

SPACE RANGE

INTEGRALS:

int 4bytes +/-2billion

short 2bytes +/-32,767

long 8bytes +/-9.2x1018

byte 1byte -129to127

FLOATING-POINT:

float 4bytes 7-8digits

double 8bytes 16-17digits

CHARACTERTYPE:

char 2bytes 65,536

BOOLEANTYPE:

boolean trueandfalse

Declaring a variable
BeforeyoucanuseavariableinaJavaprogramyoumustfirstdeclareitby
specifyingitstypeandassigningtoitaname.Thevariablenamemustbea
legalJavaidentifierandthevariabletypemustbeoneoftheprimitivedata
typeslistedin Table4-1 . Thepurposeofthedeclarationstatementistoin-
form the compiler of our intention of creating a variable of a specific type
and tagging it with a particular name. The result is that Java reserves a
memory space in which to store the data and associates it with the identi-
fier that we assigned as a name. For example, the following declaration cre-
ates a variable of type int:

int age1;