The document outlines various creational, structural, and behavioral design patterns in software development. It describes patterns such as Factory Method, Singleton, Adapter, and Observer, explaining their purposes and implementations. Each pattern is aimed at solving specific design challenges and improving code organization and maintainability.

1. Creational design patterns
●● Factory Method: Allow subclasses to “decide”
which class to instantiate.
●● Abstract Factory: Encapsulate a set of analo-
gous factories that produce families of objects.
●● Builder: Encapsulate the construction of com-
plex objects from their representation; so, the
same building process can create various repre-
sentations by specifying only type and content.
●● Singleton: Ensure that only a single instance of
a class exists and provide a single method for
gaining access to it.
●● Prototype: Create an initialized instance for
cloning or copying.

2. Factory Method
Provide an interface for the creation of objects.
Allow subclasses to “decide” which class to instantiate.
c

3. Abstract Factory
Povide an interface for creating families of related
or dependent objects. A factory for factories.
c

4. Builder
Seperate the construction process (how) of a complex object
from the concrete representations (what).
c

5. Singleton
Ensure a class only has one instance, and provide a global
point of access to it.
Oh, I’m so
loooooooonly
c

6. Prototype
Make variations on copies of a basic-object.
COPY-SERVICE
c

7. Structural design patterns
●● Adapter: Adapt an interface to an expected
interface.
●● Bridge: Decouple an interface from its
implementation.
●● Composite: Create a tree structure for
part-whole hierarchies.
●● Decorator: Extend functionality dynamically.
●● Facade: Simplify usage by defining a high-level
interface.
●● Flyweight: Support fine-grained objects
efficiently by sharing.
●● Proxy: Represent an object with another object
for access control.

8. Adapter (= Wrapper)
Adapt an interface to an expected interface.c

9. Bridge
Decouple an abstraction from its implementation.c
COLA
COLA
COLA
COLA
1 LITER
1 LITER
COLA
MILK
MILK
1 LITER
1 LITER
MILK

10. Composite
Create a tree structure for part-whole hierarchies. A node is also a
(part of a) tree. Recursive:
c

11. Decorator
Add extra functionallity (at runtime),
while keeping the interface the same.
Matroushka’s...
c

12. Facade
Provide a general (simpler) interface for a set of interfaces.
looks
simple
c

13. Flyweight
Use one instance of a class to provide many
“virtual” instances.
c

14. Proxy
Provide a surrogate or placeholder for another object
to control access to it.
c

15. Behavioral design patterns
●● Chain of Responsibility: Define a method of passing a
request among a chain of objects.
●● Command: Encapsulate a command request in an object.
●● Interpreter: Allow inclusion of language elements in an appli-
cation.
●● Iterator: Enable sequential access to collection elements.
●● Mediator: Define simplified communication between classes.
●● Memento: Save and restore the internal state of an object.
●● Observer: Define a scheme for notifying objects of changes to
another object.
●● State: Alter the behavior of an object when its state changes.
●● Strategy: Encapsulate an algorithm inside a class.
●● Template Method: Allow subclasses to redefine the steps of
an algorithm.
●● Visitor: Define a new operation on a class without changing it.

16. Command
Encapsulate a command request in an object.c
YOU,DO YOUR
TASK!
LIGHT
OFF
LIGHT
ON
TASKTASK

17. Chain of Responsibility
Define a method of passing a request among a chain of objects.c

18. Interpreter
Domain -> (little) language -> grammar -> objects
(DSL)
he means:
do this, do that,
and after finishing it,
go there!
HÉ!HÉ!
c

19. Iterator
Enable sequential access to collection elements, without showing
the underlying data-structures (array, list, records, etc)
nextnext
next
c

20. Mediator
Layer in between: communication via one object.c

21. Memento
Save and restore the internal state of an object.
ME
c

22. Observer
Notify “subscribers” of changes.
WHO?
ME
ME
MENO
c

23. State
Let an object show other methods after a change of internal
state (as if it changes it’s class).
in a.....hick......different state,
....hick....I behave differently....hick.....
c

24. Strategy
When something can be done in several ways, make those
ways interchangeable.
POSSI-
BILITIES
c

25. Template Method
The skeleton of an algorithm is fixed, but parts can be filled in
differently.
c

26. Visitor
Make a kind of plugin-possibility for methods: in that way me-
thods can be added in runtime.
printservice!
c

27. extra: Mixin
●● Used in Nooku (and a.o. in Ruby and Python)
●● a kind of abstract class that is mixed into another object
●● all methods of the mixin are now part of the object
●● handle with care: beware of tight coupling....