Data type and Wrapper class in java

DATAYPE AND WRAPPER CLASS

DATATYPE

• Java language support the concept of primitive datatype like c or c++
• If a language support primitive datatype that language cannot be a pure object oriented programming language.
• To make java language pure object oriented it supports the concept of wrapper class.
• As java language support the concept of architecture neutral the size of primitive data type is fixed for all the environment.

WRAPPER CLASS

• For each datatype java provide a predefined class ,technically known as wrapper class in java.
• Wrapper class are used to convert data type an object .In java primitive datatype are not object they don’t belongs to any class.
• All the wrapper class present in java.lang package.
• Wrapper class are also used for type conversion.
• All the wrapper class are final class it can’t be inherited.

DATATYPES	WRAPPER CLASS	SIZE	DEFAULT VALUE
byte	Byte	8bits	0
char	Character	16bits	/u
short	Short	16bits	0
int	Integer	32bits	0
long	Long	64bits	0L/0l
float	Float	32bits	0.0f
double	Double	64bits	0.0
Boolean	Boolean	1bit	false

NOTE    Signed and unsigned keyword are not available in java like c or c++,by default datatype is always signed in nature.

PARSEBYTE( ) –This is a static method present in byte wrapper class which is used to convert a string to a byte type.

TOSTRING( )- This is a predefined static method present in each wrapper class which convert a datatype to string format.

charAt( )- This method is used to get character of a specific index.

ToBinaryString( )- This method is convert integer to binary  and return value into a string format.

toOctalString( )- This method is convert integer to octal and return value into a string format.

toHexaString( )-This method is convert integer to hexadecimal and return value into a string format.

CurrentTimeMillis( )-It is a predefined static method present in system class which always return the system time in mill sec format.