Java: Integer vs int

An Integer is a class, or a reference type, defined in the standard library. It stores a reference to an object containing a value (a "box").

An int on the other hand, is a primitive type and part of the language itself. It stores an actual value.

We say that Integer is the wrapper type for int, and objects of type Integer are boxed values.

Continue reading here:

Java: Primitives vs Objects and References
Java: Wrapper Types