CS 4773 Object Oriented Systems
Midterm Review: Spring 1999

Exam Review: The exam will be closed book.

• Java in general: writing simple Java code
• The Java programming model - primitive and reference types
  e.g. What does the following code do?
• Using threads: internal and external
• Object oriented programming concepts and how they are implemented in Java
  • Responsibilities
    • Describe behavior in terms of an object in terms of what should be accomplished, rather than the method to accomplish it.
  • Encapsulation
    • The internal structure (implementation) should be hidden from the user.
    • The internal structure should also be protected from the misuser.
    • Java uses private and protected to hide structure.
  • Classes and Instances
    • An object is an instance of a class.
    • A class defines the behavior of the objects in the class.
    • In Java, variables can be either instance variables (one for each instance) or class variables (shared by all instances). Similarly for methods.
  • Class Hierarchies and Inheritance
    • Java uses extends
      • Specialization or extension: new class has all of the properties of old plus more
      • Construction: just use the methods of the parent, but these may not be visible to the outside
      • Combination (multiple inheritance): Java does not support this
      • Replacement: Java can override methods of the parent.
      • Refinement: supplementing the actions of the parent. Java uses super.
    • Java uses implements
      • Specification: methods of parent are incompletely specified
  • Assignment
    • Copy semantics: Java uses this for primitive types.
      Also, some object have a clone method.
    • Pointer semantics: Java uses this for all reference types.
    • Copy on Write: A method of implementing copy semantics
  • Equality
    • identity: Also called pointer equivalence
      Java uses this for reference types.
    • member equality: Also called structural equivalence
      Java uses this for primitives.
      Also, some objects have an equals method.
  • Polymorphism
    • Java does not support operator overloading.
    • Java does not support polymorphic variables.
    • Java does not support templates, parameterizing a class or function by use of a type.
      However, you can pass an Object as a parameter to a method, and determine the type at run time.
    • Java does support the overloading of methods.