6. wrapper classes in java.txt

Java provides wrapper classes for each of its primitive data types 
using these classes, we can treat the primitive data types as objects 

int primitiveInt = 10; //primitive integer 10
Integer wrapperInt = Integer.valueOf(10); //wrapper integer 10

key features:
since these are classes, there are methods and states which can be accessed by the objects of these wrapper classes 
these methods can convert types, parse types, and much more
unlike the primitives, these types can be null since they are references to the objects of the wrapper classes 
instances of wrapper classes are immutable 

manual conversions between the wrapper class and corresponding primitives:
-Integer wrapperInt = Integer.valueOf(primitiveInt) // primitive -> wrapper 
-int primitiveInt = wrapperInt.intValue(); // wrapper -> primitive

automatic conversion between the wrapper class and corresponding primitives:
-this is done by the compiler
-Autoboxing:
    -conversion of primitive type to wrapper 
    -it happes when we:
        -assign a primitive type to a wrapper class variable 
        -pass a primitive as a parameter to the function which expects the wrapper class variable 
        -adding primitives to collections that stores objects
-unboxing:
    -conversion of wrapper class instance to primitive data type 
    -it happes when we:
        -assign a wrapper class variable to a  primitive type
        -pass a wrapper class instance as a parameter to the function which expects the primitive type variable 
        -adding wrapper class objects to collections that stores primitives

applications:
-collections and generics can work only with objects and therefore in order to store primitives, we need the 
wrapper classes and the autoboxing and unboxing sort of concepts 
-plays important role in method overloading by accepting both the primitives and wrapper classes 

important considerations:
-Performance: Frequent boxing and unboxing can lead to performance overhead due to object creation and garbage collection.
-Null Values: Unboxing a null wrapper object results in a NullPointerException.
-Equality Checks: Be cautious when comparing wrapper objects using == and equals() since the == operator checks for reference equality, while equals() checks for value equality.