Write about Wrapper Classes in Java?

Wrapper classes:

1. Vectors can’t handle primitive data types like in , char , float , long , double.

2. vector handle only objects so wrapper classes are used to convert primitive data types in to object type.

           

Simple type             int             char             double             float             long

Wrapper type Integer Character Double Float Long

Converting Primitive Data type in to Objects:

 Integer x= new Integer(i) --> integer to integer object

 Float f= new Float(i) --> float to float object

 Long l=new Long(i) --> long to long object.

 Ex :

int i=10;

Integer x =new Integer(i)

Where i=10 is integer and x is object.

Converting Objects to Primitive Data type:

int I =  IntVal . intValue (); object to primitive integer

float f =FloatVal . floatValue (); object to primitive float

long l= LongVal . longValue (); object to primitive long

Ex :

Integer x= new Integer(10);

int i= x. intValue();

Converting numbers to string using to string( ):

S₁ = Integer . toString (i); primitive integer to string

S₁ = Float . toString (f); primitive float to string

Ex :

int i=10;

S= Integer . toString(i);

Converting String Objects to Numeric Objects:

I= Integer. valueOf(s); convert string to integer objects.

F= Float. valueOf (s);  convert string to float object.

Converting Strings to primitive numbers : In this case we can use passing methods.

int i= Integer. parseInt(str); --> convert string to integer

float f= Float.parseFloat(str); -->convert string to float

long l=Long.parseLong(str); -->convert string to long