Java Lession 2 ( Data Types, Primitive, Wrapper Class)

Data Types in java

                The Data type specifies the type of data stored in the system. Any variables declared in java have to be specified with data type and has to be declared.

There are 2 types of Data Types in java,  

Primitive Data type

Data Type	Default Value (for fields)
Byte	0
Short	0
Int	0
Long	0L
Float	0.0f
Double	0.0d
Char	'\u0000'
String (or any object)	null
Boolean	false

Wrapper Class

In Java everything is treated as an object. The wrapper class used to convert Data types into Object.

As the name says, a wrapper class wraps (encloses) around a data type and gives it an object appearance.

Wrapper classes include methods to unwrap the object and give back the data type.

Primitive Data Type	Wrapper Class
byte	Byte
short	Short
int	Integer
char	Character
boolean	Boolean
double	Double
float	Float

 

Fields (variables)

                Any Field (variable) declared in java has to specify the Data type.

                Int x,y;    //// x, y are variables of int data type and used to store numbers

                String s1,s2;   ///////// s1, s2 are variables of string type and will allow to store alphanumeric values