Wrapper class: A wrapper class is a class that provides an object representation for primitive data types. In this case, the Double class is the wrapper class for the double data type.
Autoboxing: Autoboxing is the automatic conversion of a primitive data type to its corresponding wrapper class. For example, when assigning a primitive double value to a Double variable.
Unboxing: Unboxing is the process of converting an object of a wrapper class back to its corresponding primitive data type. This happens automatically when using an operator or method that requires a primitive value.