wrapper classes in java
Wrapper classes: classes that are dedicated to primitives
Byte, Short, Integer, Long, Float, Double, Character, Boolean
presented in "java.lang" package
AutoBoxing: converting primitive values to wrapper class
int a = 100;
Integer b = a // auto boxing
Unboxing: converting wrapper class value to primitives
Integer a = 100;
int b = a; // unboxing
int a = 100;
double b = a; // none