[2][3] The primitive wrapper classes are found in the Java API.
Primitive wrapper classes are used to create an Object that needs to represent primitive types in Collection classes (i.e., in the Java API), in the java.util package and in the java.lang.reflect reflection package.
Whereas variables, for example, can be declared in Java as data types double, short, int, etc., the primitive wrapper classes create instantiated objects and methods that inherit but hide the primitive data types, not like variables that are assigned the data type values.
[4] [5] With Java 5.0, additional wrapper classes were introduced in the java.util.concurrent.atomic package.
Instead, they provide atomic operations for addition, increment and assignment.