Wrapper classes

For every primitive type in Java, there is a built-in object type called a wrapper class. For example, the wrapper class for int is called Integer; for double it is called Double.

Wrapper classes are useful for several reasons:

• You can instantiate wrapper classes and create objects that contain primitive values. In other words, you can wrap a primitive value up in an object, which is useful if you want to invoke a method that requires an object type.
• Each wrapper class contains special values (like the minimum and maximum values for the type), and methods that are useful for converting between types.