Wrapper class in java ~ foundjava

Wrapper class in Java

Wrapper class in java provides the mechanism to convert primitive into object and object into primitive.

Since J2SE 5.0, autoboxing and unboxing feature converts primitive into object and object into primitive automatically. The automatic conversion of primitive into object is known as autoboxing and vice-versa unboxing.

The eight classes of java.lang package are known as wrapper classes in java. The list of eight wrapper classes are given below:

Primitive Type	Wrapper class
boolean	Boolean
char	Character
byte	Byte
short	Short
int	Integer
long	Long
float	Float
double	Double

Wrapper class Example: Primitive to Wrapper

1. public class WrapperExample1{  
2. public static void main(String args[]){  
3. //Converting int into Integer  
4. int a=20;  
5. Integer i=Integer.valueOf(a);//converting int into Integer  
6. Integer j=a;//autoboxing, now compiler will write Integer.valueOf(a) internally  
7.   
8. System.out.println(a+" "+i+" "+j);  
9. }}  

Output:

20 20 20

Wrapper class Example: Wrapper to Primitive

1. public class WrapperExample2{    
2. public static void main(String args[]){    
3. //Converting Integer to int    
4. Integer a=new Integer(3);    
5. int i=a.intValue();//converting Integer to int  
6. int j=a;//unboxing, now compiler will write a.intValue() internally    
7.     
8. System.out.println(a+" "+i+" "+j);    
9. }}    

Output:

3 3 3