Object Orientation

• Object Oriented Programming:
  • Composition Over Inheritance
  • Alan Kay – Definition of OO
  • UML Modeling
  • OO_Concepts (pdf)
  • What people misunderstand about OOP
  • LSP vs. OCP
  • 10 Object-Oriented (OOP) Design Principles Java Programmers Should Know

History of Programming Languages

• Smalltalk:
  • Squeak
  • Smalltalk.org
  • Univ. of Michigan

Object Management Group (OMG)

• Object Relational Mapping (ORM):
  • Wikipedia
  • JPA
  • Hibernate
  • Discussions

• Inheritance:
  • Square is not a Rectangle
  • What’s wrong with Square and Rectangle inheritance?

    • A typical example that violates LSP is a Square class that derives from a Rectangle class, assuming getter and setter methods exist for both width and height.

      The Square class always assumes that the width is equal with the height. If a Square object is used in a context where a Rectangle is expected, unexpected behavior may occur because the dimensions of a Square cannot (or rather should not) be modified independently.

      This problem cannot be easily fixed: if we can modify the setter methods in the Square class so that they preserve the Square invariant (i.e., keep the dimensions equal), then these methods will weaken (violate) the postconditions for the Rectangle setters, which state that dimensions can be modified independently.

Object Orientation

Interfaces