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 · Accepted 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<HelloListener> listeners = new ArrayList<HelloListener>();

    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

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  amp  corresponding function to add remove them in the list     List lt ThrowListener gt  listeners   new ArrayList lt ThrowListener gt         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

[java] Create a custom event in Java

Examples related to java

Examples related to events

Examples related to listener

Examples related to handler