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Why do we need command patterns?
The command pattern should be used when: You need a command to have a life span independent of the original request, or if you want to queue, specify and execute requests at different times. You need undo/redo operations. The command’s execution can be stored for reversing its effects.
What is the primary advantage of using the Command pattern?
The main advantage of the command design pattern is that it decouples the object that invokes the operation from the one that know how to perform it. And this advantage must be kept. There are implementations of this design pattern in which the invoker is aware of the concrete commands classes.
How does the command pattern help us do that?
The command pattern helps us do that. Definition: The command pattern encapsulates a request as an object, thereby letting us parameterize other objects with different requests, queue or log requests, and support undoable operations. The definition is a bit confusing at first but let’s step through it.
Can a class diagram be used in UML?
The class diagram in UML can be used to capture the patterns identified in a system. In addition, UML has a sufficiently extensive and expressive vocabulary to capture the details of patterns.
Why do we use simple if-else in a command pattern?
By using simple if-else we are coding to implementation rather than interface. Also there is tight coupling. So what we want to achieve is a design that provides loose coupling and remote control should not have much information about a particular device. The command pattern helps us do that.
Which is an example of a command pattern in Java?
Below is the Java implementation of above mentioned remote control example: Notice that the remote control doesn’t know anything about turning on the stereo. That information is contained in a separate command object. This reduces the coupling between them. Makes our code extensible as we can add new commands without changing existing code.