Wrapper Class

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Wrapper class in Java

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

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

The eight classes of java .Lang package are known as wrapper classes in java. The list of eight wrapper classes is 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