wrapper class in java

wrapper class 

the primitive data type is not an object, so If we need a method that only takes objects as a parameter, it can't be used. Therefore, wrapper classes are used to convert data type into an object. 

Primitive Data Type	Wrapper instance
char	Character
byte	Byte
short	Short
long	Integer
float	Float
double	Double
boolean	Boolean

Boxing & UnBoxing 

The conversion of primitive data types into wrapper class is boxing. Whereas, converting an object into corresponding primitive data type is unboxing

Example code

public class BoxingUnBoxing
{
    public static void main(String[] args)
    {
        Integer iValue = new Integer(10);
        Double dValue = new Double(3.14);
        
        System.out.println(iValue); //10
        System.out.println(dValue); //3.14
        
        iValue = new Integer(iValue.intValue()+10);
        dValue = new Double(dValue.doubleValue()+1.2);
        
        System.out.println(iValue); //20
        System.out.println(dValue); //4.34
    } 
}

AutoBoxing & AutoUnBoxing 

Example code

public class AutoBoxingUnBoxing
{
    public static void main(String[] args)
    {
        Integer iValue = 10; //auto boxing
        Double dValue = 3.14; // aut boxing
        
        System.out.println(iValue); //10
        System.out.println(dValue); //3.14
        
        int num1 = iValue; //auto unboxing
        double num2 = dValue; //auto unboxing
        
        System.out.println(num1); //10
        System.out.println(num2); //3.14
    } 
}