Wrapper class ,auto boxing and unboxing in Java

#Topic-6
Previous topic (5) we have discussed about Variables and Data Types in Java, we have gone through various data types and literals. If you have not gone through that topic, click this link What are the Variables and Data types using in Java?
In this section we will discuss about Wrapper class, auto-boxing, UN-boxing and many more!

Wrapper class in Java

Each of Java's eight primitive data types has a class dedicated to it. These are known as wrapper classes because they "wrap" the primitive data type into an object of that class. The wrapper classes are part of the java.lang package, which is imported by default into all Java programs. 

Wrapper class in java are the Object representation of eight primitive types in java. All the wrapper classes in java are immutable and final. Java  auto boxing and UN-boxing allows easy conversion between primitive types and their corresponding wrapper classes in java programs.All the wrapper classes (Integer, Long, Byte, Double, Float, Short) are sub classes of the abstract class Number.

The following two statements illustrate the difference between a primitive data type and an object of a wrapper class:  

int a = 25; //primitive data type
Integer b = new Integer(33); //using wrapper class

The first statement declares an int variable named a and initializes it with the value 25. The second statement instantiates an Integer object. The object is initialized with the value 33 and a reference to the object is assigned to the object variable b.

Why do we need wrapper classes?

· We need wrapper classes when we need a type that will fit in the Object world programming like Collection classes. We use primitive types when we want things to be simple. 
· Primitive types can’t be null but wrapper classes can be null. 
· Achieve Auto-boxing and UN-boxing.

Auto-boxing :
Auto-boxing is a process by which primitive type is automatically encapsulated (boxed) into its equivalent type wrapper 
Example of Auto-boxing in java:
class AutoBoxingDemo{
public static void main(String args[]){
int a=50;
Integer a1=new Integer(a); //Conversion – kind of autoboxing
Integer a2=5; //it is actual AutoBoxing , we are not using any construct or method
System.out.println(a2+" "+a3); 
} 
}

UN-boxing: 
UN-boxing is a process by which the value of an object is automatically extracted from a type Wrapper class.
 Example of UN-boxing in java :
class UnboxingDemo{
public static void main(String args[]){
Integer i=new Integer(100);
int a=i; // Unboxing
System.out.println(a);
}
}

What is Next?
In the next section, we will be going through How to convert String into primitive data types and primitive data types into String.

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