The document explains the implementation of the Command Design Pattern in Java, emphasizing its role in decoupling the request for an action from the actual object performing the action. It outlines key terminology, such as client, invoker, recipient, and command, and highlights the pattern's benefits in promoting flexible and maintainable code. Additionally, the document includes a UML diagram and a sample program for better understanding and practical application.

1. How do I implement command Design pattern in the Java programming
course with example

2. Command Pattern-Terminology
UML diagram of the command Design Pattern

3. Prepared by Preeti

4. It's a good idea to save the project, because that will allow you to
change the project in case you decide to do something different with
future sliders.
There are many Java programming course tutorials that you will find to
learn design patterns, but not really talked about a particular design
pattern in depth.
So today we learn one of the important design patterns, which is often
overlooked by Java developers.

5. Yes, I'm talking about the command pattern that can help you write
flexible, loosely coupled code to implement actions and events in your
application.
In simple terms, the command design pattern is used to separate a
request for an action from the object that actually performs the action.
This decoupling between Invoker and Receiver object provides a
uniform way to perform different types of actions.
This decoupling is achieved with a command object, which is usually
an interface to methods such as execute ().

6. The Requestor or Invoker only knows Command object and does not
care about the actual object that processes the request, which may be
different. This transparency leads to cleaner code on the Invoker page
and also allows the ability to do several intelligent things on the
command page.
Your command object can be so stupid, how the request delegate to the
recipient and can be as smart as the record of the last command for
implementing UNDO and Redo functionality.

7. The command pattern ensures that your code with the open closed
design principle, the O of SOLID design principles, compliant, which
means that adding a new command would be very easy to create a new
implementation of the Command interface and the Invoker code is not
affected.
https://www.exltech.in/java-training.html
The Command pattern is popular in GUI applications, where we use a
lot of commands, e.g. Open, Close, Save, cut, Copy, Paste, and
appropriate UNDO and REDO operations. You can also see the Java
Design Patterns Masterclass, which not only covers command patterns
and has recently been updated to Java SE 8.

8. 1. Command Pattern-Terminology
Before proceeding and implementing a command pattern in Java, we
will familiarize ourselves with the terminology used in this pattern.
Client-creates concrete command object and configure with recipient
Invoker-Who hold command, and calls execute () method on the
Command object
Recipient-actual object that processes the request
Command-Interface that handles the request from the Invoker and
delegates it to the recipient
ConcreteCommand - implementation of the command interface for a
specific task

9. UML diagram of the command Design Pattern
Here is the UML diagram of the command design pattern, that makes
things clearer.
You can see that the Client has a reference to a callback interface that
has a generic method execute(). The individual commands implement
this interface and provide an implementation, which is nothing else than
delegating to the actual object.

10. The most important thing is that the client does not know about the
actual object that performs an action on behalf of these commands. This
decoupling leads to flexible code and makes it easy to add new
commands without affecting the client code.
2. Command design pattern in Java-example
Here is our sample program to demonstrate how to use the command
pattern in Java.
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