Data Types

In Java, data types specify the size and type of values that can be stored in variables. Java has two categories of data types: Primitive data types and Reference data types.

Primitive Data Type

Primitive data types are predefined by the language and are named by a reserved keyword. They represent single values and are not objects.

Different Types

Data Type	Description	Size	Default Value
byte	8-bit signed integer	1 byte	0
short	16-bit signed integer	2 bytes	0
int	32-bit signed integer	4 bytes	0
long	64-bit signed integer	8 bytes	0L
float	32-bit floating point	4 bytes	0.0f
double	64-bit floating point	8 bytes	0.0d
char	16-bit Unicode character	2 bytes	'\u0000'
boolean	true or false	not precisely defined	false

Limits or Range

Data Type	Size (in bits)	Minimum Value	Maximum Value
byte	8	-128	127
short	16	-32,768	32,767
int	32	-2,147,483,648	2,147,483,647
long	64	-9,223,372,036,854,775,808	9,223,372,036,854,775,807
float	32	Approximately ±3.40282347E+38F	Approximately ±1.40239846E-45F
double	64	Approximately ±1.7976931348623157E+308	Approximately ±4.94065645841246544E-324
char	16	0	65,535
boolean	not precisely defined	true or false	true or false

Size of data types is constant in java. The JVM (Java Virtual Machine) is designed to be platform independent. If data type sizes were different across platforms, then cross-platform consistency is sacrificed. The JVM isolates the program from the underlying OS and platform.

Reference Data Types:

Reference data types are objects that hold references to the memory location where the data is stored. They include classes, interfaces, arrays, and enumerations.

Primitive Wrapper Classes:

These are reference data types that wrap primitive data types into objects. For example:

• Byte

• Short

• Integer

• Long

• Float

• Double

• Character

• Boolean

These wrapper classes are useful when working with collections or when you need to treat primitive types as objects.