The document discusses the Command design pattern, which encapsulates requests as objects so that different requests can be parameterized, queued, logged, or made undoable. The pattern addresses the need to issue requests without knowing the operation or receiver. A command defines an interface for executing an operation, concrete commands bind a receiver to an action, and a client creates concrete commands while an invoker carries out the request.

1. Command Design
Pattern
Name:- KANZARIYA ANIL
Roll no :- 11708201
Subject :- Design Pattern

2. Index
 Intent
 Motivation
 Also Known As
 Structure
 Class Diagram
 Example

3. Intent
A request is encapsulated as an object,
allowing the parameterization of clients with
different requests, queuing or logging of
requests, and supporting undoable
operations

4. Motivation
 Sometimes it is necessary to issue requests to
objects without knowing anything about the operation
being requested or the receiver of the request."
 The Command design pattern suggests
encapsulating ("wrapping") in an object all (or some)
of the following: an object, a method name, and
some arguments.
 Java does not support "pointers to methods", but its
reflection capability will do nicely. The "command" is
a black box to the "client". All the client does is call
"execute()" on the opaque object.

5. Problem
 Need to issue requests to objects without
knowing anything about the operation being
requested or the receiver of the request.

6. Also Known As
Action , Transaction

7. Structure Diagram

8. Participants
Command
• Declares an interface for executing an operation.
Concrete Command
• Defines a binding between a Receiver object and
an action.
• implements Execute by invoking the
corresponding operation(s) on Receiver.
Client
• creates a Concrete Command object and sets its
receiver.

9. Participants
Invoker
• o asks the command to carry out the request.
Receiver
• o knows how to perform the operations
associated with carrying out a request. Any class
may serve as a Receiver.

10. Class Diagram