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Command Pattern

Command Pattern. Chihung Liao Cynthia Jiang. Order Execute(). Waiter. Hamburger Execute(). Hot Dogs Execute(). Fries Execute(). Cook Make Food(). Order Execute(). Abstract command (superclass). Hamburger Execute(). Hot Dog Execute(). Fries Execute(). Concrete command

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Command Pattern

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  1. Command Pattern Chihung Liao Cynthia Jiang

  2. Order Execute() Waiter Hamburger Execute() Hot Dogs Execute() Fries Execute() Cook Make Food()

  3. Order Execute() Abstract command (superclass) Hamburger Execute() Hot Dog Execute() Fries Execute() Concrete command (subclass)

  4. Command Execute() Client Invoker Receiver Action() ConcreteCommand Execute() State

  5. Flexibility and Extensibility • Encapsulate a request as an object • Compare to C function pointer • Decouple the client and receiver by the invoker who ONLY invoke an operation • Any request can be cancelled or added in form of stack • Request to be executed can be stored as a queue

  6. Translate into JAVA 1 • Interface Command: an interface for executing an operation (it could also be an abstract class, refer to the sample code’s comment) • Class Client: creates a ConcreteCommand object and set its receiver • Class Receiver: who actually DOES things

  7. Translate into JAVA 2 • Class Invoker: ask Command to carry out an execution, an agent between ConcreteCommand and Client • Class ConcreteCommand implements Command: MUST have the method in Interface Command

  8. QUESTIONS

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