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read.me and the diagram is added
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‎event-queue/README.md‎

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---
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layout: pattern
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title: Event Queue
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folder: event-queue
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permalink: /patterns/event-queue/
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categories: Concurrency
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tags:
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- Java
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- Difficulty Intermediate
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- Queue
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---
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## Intent
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Event Queue is a good pattern if You have a limited accesibility resource (for example:
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Audio or Database), but You need to handle all the requests that want to use that.
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It puts all the requests in a queue and process them asynchronously.
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Gives the resource for the event when it is the next in the queue and in same time
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removes it from the queue.
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![alt text](./etc/model.png "Event Queue")
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## Applicability
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Use the Event Queue pattern when
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* You have a limited accesibility resource and the asynchronous process is acceptable to reach that
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## Credits
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* [Mihály Kuprivecz - Event Queue]

‎event-queue/etc/event-queue.urm.puml‎

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@startuml
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package com.iluwatar.event.queue {
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class App {
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+ App()
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+ getAudioStream(filePath : String) : AudioInputStream {static}
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+ main(args : String[]) {static}
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}
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class Audio {
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- MAX_PENDING : int {static}
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- headIndex : int {static}
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- pendingAudio : PlayMessage[] {static}
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- tailIndex : int {static}
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- updateThread : Thread {static}
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+ Audio()
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+ init() {static}
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+ playSound(stream : AudioInputStream, volume : float) {static}
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+ stopService() {static}
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+ update() {static}
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}
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class PlayMessage {
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~ stream : AudioInputStream
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~ volume : float
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+ PlayMessage()
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}
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}
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@enduml

‎event-queue/etc/model.png‎

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‎event-queue/model.png‎

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‎event-queue/model.ucls‎

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<?xml version="1.0" encoding="UTF-8"?>
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<class-diagram version="1.2.0" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true"
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realizations="true" associations="true" dependencies="false" nesting-relationships="true" router="FAN">
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<class id="1" language="java" name="com.iluwatar.event.queue.Audio" project="event-queue"
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file="/event-queue/src/main/java/com/iluwatar/event/queue/Audio.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="285" y="179"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</class>
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<class id="2" language="java" name="com.iluwatar.event.queue.PlayMessage" project="event-queue"
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file="/event-queue/src/main/java/com/iluwatar/event/queue/PlayMessage.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="633" y="179"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</class>
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<association id="3">
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<end type="SOURCE" refId="1" navigable="false">
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<attribute id="4" name="pendingAudio"/>
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<multiplicity id="5" minimum="0" maximum="2147483647"/>
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</end>
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<end type="TARGET" refId="2" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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</association>
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<classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</classifier-display>
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<association-display labels="true" multiplicity="true"/>
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</class-diagram>

‎event-queue/src/main/java/com/iluwatar/event/queue/Audio.java‎

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private static PlayMessage[] pendingAudio = new PlayMessage[MAX_PENDING];
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public static boolean isServiceRunning() {
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return updateThread.isAlive();
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}
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/**
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* This method stops the Update Method's thread.
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*/
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try {
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clip = AudioSystem.getClip();
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clip.open(pendingAudio[headIndex].stream);
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clip.start();
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headIndex++;
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} catch (LineUnavailableException e) {
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System.err.println("Error occoured while loading the audio: The line is unavailable");
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e.printStackTrace();
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} catch (IOException e) {
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System.err.println("Input/Output error while loading the audio");
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e.printStackTrace();
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}
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clip.start();
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headIndex++;
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}
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}

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