Design patterns

• abstract solution to specific problem

Creational

• create / manage creations

Structural

Behavioral

Observer pattern

• subject has list of observers
• notifies observers on change
• observer changes dependant on the change (instead of periodically asking whether the subject changed)

Facade pattern

• If you have subsystem it makes sense to have only one entrance to the subsystem
• “gate keeper”

Adapter

SOLID

• Single responsibility
• Open/closed
• Liskov substitution
• Interface segregation
• Dependency inversion

Single responsibility principle

• each class should have single responsibility

Open/closed principle

• Opened for extension, but closed for modification.
• Use inheritance and interface

Liskov substitution principle

• Objects of type T may be replaced with objects of type S

Dependency inversion principle

• create interface between dependency relationship

Sequence diagrams

• we care a lot about those in exam