Create a custom event in Java

Question

I want to do something like this in Java but I don t know the way   When event  object 1 say  hello   happens  then object 2 responds to that event by saying  hello    Can somebody give me a hint or sample code

User · Answer

There are 3 different ways you may wish to set this up:

Thrower inside of Catcher
Catcher inside of Thrower
Thrower and Catcher inside of another class in this example Test

THE WORKING GITHUB EXAMPLE I AM CITING Defaults to Option 3, to try the others simply uncomment the "Optional" code block of the class you want to be main, and set that class as the ${Main-Class} variable in the build.xml file:

4 Things needed on throwing side code:

import java.util.*;//import of java.util.event

//Declaration of the event's interface type, OR import of the interface,
//OR declared somewhere else in the package
interface ThrowListener {
    public void Catch();
}
/*_____________________________________________________________*/class Thrower {
//list of catchers & corresponding function to add/remove them in the list
    List<ThrowListener> listeners = new ArrayList<ThrowListener>();
    public void addThrowListener(ThrowListener toAdd){ listeners.add(toAdd); }
    //Set of functions that Throw Events.
        public void Throw(){ for (ThrowListener hl : listeners) hl.Catch();
            System.out.println("Something thrown");
        }
////Optional: 2 things to send events to a class that is a member of the current class
. . . go to github link to see this code . . .
}

2 Things needed in a class file to receive events from a class

/*_______________________________________________________________*/class Catcher
implements ThrowListener {//implement added to class
//Set of @Override functions that Catch Events
    @Override public void Catch() {
        System.out.println("I caught something!!");
    }
////Optional: 2 things to receive events from a class that is a member of the current class
. . . go to github link to see this code . . .
}

User · Answer

You probably want to look into the observer pattern   Here s some sample code to get yourself started   import java util        An interface to be implemented by everyone interested in  Hello  events interface HelloListener       void someoneSaidHello          Someone who says  Hello  class Initiater       private List lt HelloListener gt  listeners   new ArrayList lt HelloListener gt          public void addListener HelloListener toAdd            listeners add toAdd              public void sayHello             System out println  Hello                  Notify everybody that may be interested          for  HelloListener hl   listeners              hl someoneSaidHello                Someone interested in  Hello  events class Responder implements HelloListener        Override     public void someoneSaidHello             System out println  Hello there                class Test       public static void main String   args            Initiater initiater   new Initiater            Responder responder   new Responder             initiater addListener responder            initiater sayHello        Prints  Hello     and  Hello there                 Related article  Java  Creating a custom event

User · Answer

The following is not exactly the same but similar  I was searching for a snippet to add a call to the interface method  but found this question  so I decided to add this snippet for those who were searching for it like me and found this question    public class MyClass                  class code goes here          public interface DataLoadFinishedListener               public void onDataLoadFinishedListener int data type                      private DataLoadFinishedListener m lDataLoadFinished           public void setDataLoadFinishedListener DataLoadFinishedListener dlf               this m lDataLoadFinished   dlf                       private void someOtherMethodOfMyClass                         m lDataLoadFinished onDataLoadFinishedListener 1                         Usage is as follows   myClassObj setDataLoadFinishedListener new MyClass DataLoadFinishedListener                  Override             public void onDataLoadFinishedListener int data type

User · Answer

What you want is an implementation of the observer pattern  You can do it yourself completely  or use java classes like java util Observer and java util Observable

[java] Create a custom event in Java

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