Java Programming Tutorial - 5 - Variables

What is a variable?

A variable is a container that stores a meaningful value that can be used throughout a program. For example one variable that stores the regular price of an item for calculating tax on it. Variables store this information in a computer's memory and the value of a variable can change all through out a program.

Declaring variables

Use these keywords when declaring your variables to set the data type of the variable.

Java data types

Keyword	Type of data the variable will store	Size in memory
boolean	true/false value	1 bit
byte	byte size integer	8 bits
char	a single character	16 bits
double	double precision floating point decimal number	64 bits
float	single precision floating point decimal number	32 bits
int	a whole number	32 bits
long	a whole number (used for long numbers)	64 bits
short	a whole number (used for short numbers)	16 bits

Example:

char aCharacter; int aNumber;

You can assign a value to a variable at the same time that it is declared. This process is known as initialization:

Example:

char aCharacter = 'a'; int aNumber = 10;

Declaring a variable and then giving it a value:

char aCharacter; aCharacter = 'a'; int aNumber; aNumber = 10;

NOTE: A variable must be declared with a data type or an error will be generated!

Naming variables

Rules that must be followed when naming variables or errors will be generated and your program will not work:

• No spaces in variable names
• No special symbols in variable names such as !@#%^&*
• Variable names can only contain letters, numbers, and the underscore ( _ ) symbol
• Variable names can not start with numbers, only letters or the underscore ( _ ) symbol (but variable names can contain numbers)

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