Wrapper classes in Java

    The wrapper class in Java provides the mechanism to convert primitive into object and object into primitive. While primitive data types are more efficient in terms of memory and performance, they lack certain features that are available for objects.

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

The list of eight wrapper classes are given below:

• Autoboxing:

//Java program to convert primitive into objects

//Autoboxing example of int to Integer

public class WrapperExample1{

public static void main(String args[]){

//Converting int into Integer

int a=20;

Integer i=Integer.valueOf(a);//converting int into Integer explicitly

Integer j=a;//autoboxing, now compiler will write Integer.valueOf(a) internally

System.out.println(a+" "+i+" "+j);

}}

• Unboxing:

//Java program to convert object into primitives

//Unboxing example of Integer to int

public class WrapperExample2{

public static void main(String args[]){

//Converting Integer to int

Integer a=new Integer(3);

int i=a.intValue();//converting Integer to int explicitly

int j=a;//unboxing, now compiler will write a.intValue() internally

System.out.println(a+" "+i+" "+j);

}}