Autoboxing

Autoboxing & Unboxing

Agenda

Wrapper Classes
Autoboxing
Unboxing

Wrapper Classes

Java Wrapper classes provide a mechanism to use primitive data types as objects.

Wrapper Classes

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

Wrapper Classes

Why do we need wrapper classes ?

Collections
The Java collections require objects instead of primitive types.

import java.util.ArrayList;

class Main {
    public static void main(String[] args) {
        ArrayList<int> arr = new ArrayList<int>();  // Error
    }
}

Wrapper Classes

Why do we need wrapper classes ?

Collections
The Java collections require objects instead of primitive types.

import java.util.ArrayList;

class Main {
    public static void main(String[] args) {
        ArrayList<Integer> arr = new ArrayList<Integer>();
    }
}

Wrapper Classes

Why do we need wrapper classes ?

2. Synchronization
Java synchronization works with objects in Multithreading.

Autoboxing is the automatic conversion that the Java compiler makes between the primitive types and their corresponding object wrapper classes.

Autoboxing

class Main {
    public static void main(String[] args) {
        int x = 5;
        float y = 3.14F;
        long z = 10000;
        
        Integer intObj = x;
        Float floatObj = y;
        Long longObj = z;
    }
}

The automatic conversion of a wrapper object to its corresponding primitive data type is known as Unboxing.

Unboxing

class Main {
    public static void main(String[] args) {
        Integer x = 5;
        Float y = 2.4F;
        Long z = 10000L;
        
        int a = x;
        float b = y;
        long c = z;
    }
}