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Merge pull request iluwatar#276 from hoswey/master
iluwatar#271 implements producer-consumer
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‎pom.xml‎

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<module>execute-around</module>
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<module>property</module>
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<module>intercepting-filter</module>
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<module>producer-consumer</module>
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<module>poison-pill</module>
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<module>lazy-loading</module>
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<module>service-layer</module>

‎producer-consumer/etc/producer-consumer.png‎

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‎producer-consumer/etc/producer-consumer.ucls‎

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<?xml version="1.0" encoding="UTF-8"?>
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<class-diagram version="1.1.8" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true"
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realizations="true" associations="true" dependencies="false" nesting-relationships="true">
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<class id="1" language="java" name="com.iluwatar.producer.consumer.Item" project="producer-consumer"
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file="/producer-consumer/src/main/java/com/iluwatar/producer/consumer/Item.java" binary="false"
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corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="415" y="378"/>
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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.producer.consumer.Producer" project="producer-consumer"
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file="/producer-consumer/src/main/java/com/iluwatar/producer/consumer/Producer.java" binary="false"
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corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="150" y="191"/>
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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="3" language="java" name="com.iluwatar.producer.consumer.Consumer" project="producer-consumer"
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file="/producer-consumer/src/main/java/com/iluwatar/producer/consumer/Consumer.java" binary="false"
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corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="675" y="186"/>
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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="4" language="java" name="com.iluwatar.producer.consumer.ItemQueue" project="producer-consumer"
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file="/producer-consumer/src/main/java/com/iluwatar/producer/consumer/ItemQueue.java" binary="false"
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corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="415" y="187"/>
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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="5">
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<end type="SOURCE" refId="3" navigable="false">
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<attribute id="6" name="queue"/>
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<multiplicity id="7" minimum="0" maximum="1"/>
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</end>
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<end type="TARGET" refId="4" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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</association>
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<association id="8">
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<end type="SOURCE" refId="4" navigable="false">
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<attribute id="9" name="queue"/>
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<multiplicity id="10" minimum="0" maximum="2147483647"/>
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</end>
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<end type="TARGET" refId="1" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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</association>
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<association id="11">
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<end type="SOURCE" refId="2" navigable="false">
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<attribute id="12" name="queue"/>
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<multiplicity id="13" minimum="0" maximum="1"/>
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</end>
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<end type="TARGET" refId="4" 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>

‎producer-consumer/index.md‎

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---
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layout: pattern
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title: Producer Consumer
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folder: producer-consumer
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permalink: /patterns/producer-consumer/
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categories: Other
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tags: Java
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---
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**Intent:** Producer Consumer Design pattern is a classic concurrency or threading pattern which reduces
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coupling between Producer and Consumer by separating Identification of work with Execution of
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Work..
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![alt text](./etc/producer-consumer.png "Producer Consumer")
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**Applicability:** Use the Producer Consumer idiom when
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* decouple system by separate work in two process produce and consume.
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* addresses the issue of different timing require to produce work or consuming work
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‎producer-consumer/pom.xml‎

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<?xml version="1.0"?>
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<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<groupId>com.iluwatar</groupId>
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<artifactId>java-design-patterns</artifactId>
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<version>1.7.0</version>
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</parent>
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<artifactId>producer-consumer</artifactId>
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<dependencies>
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<scope>test</scope>
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</dependency>
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</dependencies>
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</project>

‎producer-consumer/src/main/java/com/iluwatar/producer/consumer/App.java‎

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package com.iluwatar.producer.consumer;
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import java.util.concurrent.ExecutorService;
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import java.util.concurrent.Executors;
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import java.util.concurrent.TimeUnit;
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/**
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* Producer Consumer Design pattern is a classic concurrency or threading pattern which reduces
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* coupling between Producer and Consumer by separating Identification of work with Execution of
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* Work.
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* <p>
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* In producer consumer design pattern a shared queue is used to control the flow and this
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* separation allows you to code producer and consumer separately. It also addresses the issue of
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* different timing require to produce item or consuming item. by using producer consumer pattern
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* both Producer and Consumer Thread can work with different speed.
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*
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*/
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public class App {
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/**
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* Program entry point
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*
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* @param args command line args
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*/
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public static void main(String[] args) {
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ItemQueue queue = new ItemQueue();
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ExecutorService executorService = Executors.newFixedThreadPool(5);
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for (int i = 0; i < 2; i++) {
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final Producer producer = new Producer("Producer_" + i, queue);
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executorService.submit(() -> {
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while (true) {
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producer.produce();
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}
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});
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};
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for (int i = 0; i < 3; i++) {
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final Consumer consumer = new Consumer("Consumer_" + i, queue);
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executorService.submit(() -> {
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while (true) {
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consumer.consume();
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}
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});
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}
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executorService.shutdown();
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try {
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executorService.awaitTermination(10, TimeUnit.SECONDS);
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executorService.shutdownNow();
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} catch (InterruptedException e) {
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System.out.println("Error waiting for ExecutorService shutdown");
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}
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}
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}

‎producer-consumer/src/main/java/com/iluwatar/producer/consumer/Consumer.java‎

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package com.iluwatar.producer.consumer;
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/**
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* Class responsible for consume the {@link Item} produced by {@link Producer}
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*/
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public class Consumer {
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private final ItemQueue queue;
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private final String name;
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public Consumer(String name, ItemQueue queue) {
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this.name = name;
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this.queue = queue;
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}
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public void consume() throws InterruptedException {
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Item item = queue.take();
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System.out.println(String.format("Consumer [%s] consume item [%s] produced by [%s]", name,
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item.getId(), item.getProducer()));
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}
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}

‎producer-consumer/src/main/java/com/iluwatar/producer/consumer/Item.java‎

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package com.iluwatar.producer.consumer;
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/**
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* Class take part of an {@link Producer}-{@link Consumer} exchange.
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*/
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public class Item {
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private String producer;
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private int id;
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public Item(String producer, int id) {
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this.id = id;
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this.producer = producer;
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}
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public int getId() {
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return id;
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}
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public String getProducer() {
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return producer;
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}
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}

‎producer-consumer/src/main/java/com/iluwatar/producer/consumer/ItemQueue.java‎

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package com.iluwatar.producer.consumer;
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import java.util.concurrent.LinkedBlockingQueue;
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/**
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* Class as a channel for {@link Producer}-{@link Consumer} exchange.
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*/
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public class ItemQueue {
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private LinkedBlockingQueue<Item> queue;
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public ItemQueue() {
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queue = new LinkedBlockingQueue<Item>(5);
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}
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public void put(Item item) throws InterruptedException {
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queue.put(item);
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}
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public Item take() throws InterruptedException {
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return queue.take();
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}
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}

‎producer-consumer/src/main/java/com/iluwatar/producer/consumer/Producer.java‎

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package com.iluwatar.producer.consumer;
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import java.util.Random;
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/**
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* Class responsible for producing unit of work that can be expressed as {@link Item} and submitted
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* to queue
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*/
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public class Producer {
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private final ItemQueue queue;
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private final String name;
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private int itemId = 0;
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public Producer(String name, ItemQueue queue) {
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this.name = name;
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this.queue = queue;
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}
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public void produce() throws InterruptedException {
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Item item = new Item(name, itemId++);
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queue.put(item);
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Random random = new Random();
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Thread.sleep(random.nextInt(2000));
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}
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}

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