Friday 10 February, 2012

Java Data Types

Java has two groups of data types, primitive data types and object references.

Java Primitive Data Types

Data Type	Purpose	Contents	Default Value*
boolean	Truth value	true or false	fales
char	Character	Unicode characters	u0000
byte	Signed integer	8 bit two’s complement	(byte) 0
short	Signed integer	16 bit two’s complement	(short) 0
int	Signed integer	32 bit two’s complement	0
long	Signed integer	64 bit two’s complement	0L
float	Real number	32 bit IEEE 754 floating point	0.0f
double	Real number	64 bit IEEE 754 floating point	0.0d

One way to remember the Java primitive data types is by using this mnemonic aid: Be Careful, Bears Shouldn’t Ingest Large Furry Dogs.

* Instance variables are assigned default values; local variables are not assigned default values.

Java object references are variables which hold references to objects.

Unlike Java primitive data types which store actual data, object references store only a reference to the actual data object.