The Java class unit is used in Java for several different purposes:

• The class has the main method for an application program

• The class is a container for a collection of utility methods

• The class defines a type that represents concrete or abstract objects in some application/problem context.

• The class defines a type that doesn't correspond directly to the kind of objects in an application/problem.

  However, such a class may be useful in applications - for example, to store application objects or to help process application objects.