JAVA: Generic exercise
Overview:
Create a generic SignalListener interface whichrecieves signals.
Create the generic SignalFetcher class whichimplements SignalListener and prints a message whenever a signal isreceived.
Create the generic SignalSender class whichlets you attach any number of SignalListener objects and send asignal to all of them; furthermore, when the signal is sent to eachof the listeners, it is done in order based on a key value.
Background:
There are often cases when you need to send signals from oneobject to another. For example, if you click on a button in youruser interface, some other part of your code may react to it. Or,if you are monitoring
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