There are two kinds of variable types in
Java: primitive types and reference types.
The primitive types are: byte, short, int, long, char, float, double, boolean
See
The Java Tutorial: Primitive Types For each primitive type, there is a corresponding class in the Java API: Byte, Short, Integer, Long, Character, Float, Double, Boolean.
Note that in Java, primitive types are not objects. But sometimes you need an object; for example, the collection classes like ArrayList can only store objects, not primitive types. If you want to store integers in an ArrayList, you need to put those integers in objects, because you can't store
ints directly into the ArrayList. That's what you use the Integer wrapper class for: to create an object to contain the int.