Wrapper class (autoboxing, unboxing)

 Wrapper class

• The wrapper class in Java provides the mechanism to convert primitive into object and object into primitive.

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

Autoboxing: The automatic conversion of primitive data type into its corresponding wrapper class is known as autoboxing, for example, byte to Byte, char to Character, int to Integer, long to Long, float to Float, boolean to Boolean, double to Double, and short to Short.

Unboxing: The automatic conversion of wrapper type into its corresponding primitive type is known as unboxing. It is the reverse process of autoboxing.

Example of Autoboxing & Unboxing

public class WrapperClass {
    public static void main(String[] args) {
        //Converting int into Integer (autoboxing)
        int i = 10;
        Integer x = Integer.valueOf(i); //converting int into Integer explicitly
        Integer y = i; //autoboxing, now compiler will write Integer.valueOf(a) internally

        System.out.println(i+" "+x+" "+y);

        //Converting Integer to int (unboxing)
        Integer q = new Integer(20);
        int z = q.intValue(); //converting Integer to int explicitly
        int a = q; //unboxing, now compiler will write a.intValue() internally

        System.out.println(q+" "+z+" "+a);
        
    }
}

Conversion between String and Primitive Data type

public class StringPrimitive {
    public static void main(String[] args) {

        //Converting primitive to string
        int i = 234;
        String s = Integer.toString(i);
        System.out.println("S = "+s);

        //Converting String to primitive
        String st = "343";
        int in = Integer.parseInt(st);
        //int in = Integer.valueOf(st);
        System.out.println("IN = "+in);

    }
}