#271 implements producer-consumer

pom.xml

@@ -56,6 +56,7 @@
 		<module>execute-around</module>
 		<module>property</module>
 		<module>intercepting-filter</module>
+		<module>producer-consumer</module>
 		<module>poison-pill</module>
 		<module>lazy-loading</module>
 		<module>service-layer</module>

producer-consumer/etc/producer-consumer.ucls

@@ -0,0 +1,74 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<class-diagram version="1.1.8" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true" 
+  realizations="true" associations="true" dependencies="false" nesting-relationships="true">  
+  <class id="1" language="java" name="com.iluwatar.producer.consumer.Item" project="producer-consumer" 
+    file="/producer-consumer/src/main/java/com/iluwatar/producer/consumer/Item.java" binary="false" 
+    corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="415" y="378"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <class id="2" language="java" name="com.iluwatar.producer.consumer.Producer" project="producer-consumer" 
+    file="/producer-consumer/src/main/java/com/iluwatar/producer/consumer/Producer.java" binary="false" 
+    corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="150" y="191"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <class id="3" language="java" name="com.iluwatar.producer.consumer.Consumer" project="producer-consumer" 
+    file="/producer-consumer/src/main/java/com/iluwatar/producer/consumer/Consumer.java" binary="false" 
+    corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="675" y="186"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <class id="4" language="java" name="com.iluwatar.producer.consumer.ItemQueue" project="producer-consumer" 
+    file="/producer-consumer/src/main/java/com/iluwatar/producer/consumer/ItemQueue.java" binary="false" 
+    corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="415" y="187"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <association id="5">    
+    <end type="SOURCE" refId="3" navigable="false">      
+      <attribute id="6" name="queue"/>      
+      <multiplicity id="7" minimum="0" maximum="1"/>    
+    </end>    
+    <end type="TARGET" refId="4" navigable="true"/>    
+    <display labels="true" multiplicity="true"/>  
+  </association>  
+  <association id="8">    
+    <end type="SOURCE" refId="4" navigable="false">      
+      <attribute id="9" name="queue"/>      
+      <multiplicity id="10" minimum="0" maximum="2147483647"/>    
+    </end>    
+    <end type="TARGET" refId="1" navigable="true"/>    
+    <display labels="true" multiplicity="true"/>  
+  </association>  
+  <association id="11">    
+    <end type="SOURCE" refId="2" navigable="false">      
+      <attribute id="12" name="queue"/>      
+      <multiplicity id="13" minimum="0" maximum="1"/>    
+    </end>    
+    <end type="TARGET" refId="4" navigable="true"/>    
+    <display labels="true" multiplicity="true"/>  
+  </association>  
+  <classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+    sort-features="false" accessors="true" visibility="true">    
+    <attributes public="true" package="true" protected="true" private="true" static="true"/>    
+    <operations public="true" package="true" protected="true" private="true" static="true"/>  
+  </classifier-display>  
+  <association-display labels="true" multiplicity="true"/>
+</class-diagram>

producer-consumer/index.md

@@ -0,0 +1,22 @@
+---
+layout: pattern
+title: Producer Consumer
+folder: producer-consumer
+permalink: /patterns/producer-consumer/
+categories: Other
+tags: Java
+---
+
+**Intent:** Producer Consumer Design pattern is a classic concurrency or threading pattern which reduces
+ coupling between Producer and Consumer by separating Identification of work with Execution of
+ Work..
+
+
+
+![alt text](./etc/producer-consumer.png "Producer Consumer")
+
+**Applicability:** Use the Producer Consumer idiom when
+
+* decouple system by separate work in two process produce and consume.
+* addresses the issue of different timing require to produce work or consuming work
+

producer-consumer/pom.xml

@@ -0,0 +1,18 @@
+<?xml version="1.0"?>
+<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"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.iluwatar</groupId>
+    <artifactId>java-design-patterns</artifactId>
+    <version>1.7.0</version>
+  </parent>
+  <artifactId>producer-consumer</artifactId>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+</project>

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

@@ -0,0 +1,57 @@
+package com.iluwatar.producer.consumer;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Producer Consumer Design pattern is a classic concurrency or threading pattern which reduces
+ * coupling between Producer and Consumer by separating Identification of work with Execution of
+ * Work.
+ * <p>
+ * In producer consumer design pattern a shared queue is used to control the flow and this
+ * separation allows you to code producer and consumer separately. It also addresses the issue of
+ * different timing require to produce item or consuming item. by using producer consumer pattern
+ * both Producer and Consumer Thread can work with different speed.
+ * 
+ */
+public class App {
+
+  /**
+   * Program entry point
+   * 
+   * @param args command line args
+   */
+  public static void main(String[] args) {
+
+    ItemQueue queue = new ItemQueue();
+
+    ExecutorService executorService = Executors.newFixedThreadPool(5);
+    for (int i = 0; i < 2; i++) {
+
+      final Producer producer = new Producer("Producer_" + i, queue);
+      executorService.submit(() -> {
+        while (true) {
+          producer.produce();
+        }
+      });
+    };
+
+    for (int i = 0; i < 3; i++) {
+      final Consumer consumer = new Consumer("Consumer_" + i, queue);
+      executorService.submit(() -> {
+        while (true) {
+          consumer.consume();
+        }
+      });
+    }
+
+    executorService.shutdown();
+    try {
+      executorService.awaitTermination(10, TimeUnit.SECONDS);
+      executorService.shutdownNow();
+    } catch (InterruptedException e) {
+      System.out.println("Error waiting for ExecutorService shutdown");
+    }
+  }
+}

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

@@ -0,0 +1,24 @@
+package com.iluwatar.producer.consumer;
+
+/**
+ * Class responsible for consume the {@link Item} produced by {@link Producer}
+ */
+public class Consumer {
+
+  private final ItemQueue queue;
+
+  private final String name;
+
+  public Consumer(String name, ItemQueue queue) {
+    this.name = name;
+    this.queue = queue;
+  }
+
+  public void consume() throws InterruptedException {
+
+    Item item = queue.take();
+    System.out.println(String.format("Consumer [%s] consume item [%s] produced by [%s]", name,
+        item.getId(), item.getProducer()));
+
+  }
+}

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

@@ -0,0 +1,27 @@
+package com.iluwatar.producer.consumer;
+
+/**
+ * Class take part of an {@link Producer}-{@link Consumer} exchange.
+ */
+public class Item {
+
+  private String producer;
+
+  private int id;
+
+  public Item(String producer, int id) {
+    this.id = id;
+    this.producer = producer;
+  }
+
+  public int getId() {
+
+    return id;
+  }
+
+  public String getProducer() {
+
+    return producer;
+  }
+
+}

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

@@ -0,0 +1,27 @@
+package com.iluwatar.producer.consumer;
+
+import java.util.concurrent.LinkedBlockingQueue;
+
+/**
+ * Class as a channel for {@link Producer}-{@link Consumer} exchange.
+ */
+public class ItemQueue {
+
+  private LinkedBlockingQueue<Item> queue;
+
+  public ItemQueue() {
+
+    queue = new LinkedBlockingQueue<Item>(5);
+  }
+
+  public void put(Item item) throws InterruptedException {
+
+    queue.put(item);
+  }
+
+  public Item take() throws InterruptedException {
+
+    return queue.take();
+  }
+
+}

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

@@ -0,0 +1,29 @@
+package com.iluwatar.producer.consumer;
+
+import java.util.Random;
+
+/**
+ * Class responsible for producing unit of work that can be expressed as {@link Item} and submitted
+ * to queue
+ */
+public class Producer {
+
+  private final ItemQueue queue;
+
+  private final String name;
+
+  private int itemId = 0;
+
+  public Producer(String name, ItemQueue queue) {
+    this.name = name;
+    this.queue = queue;
+  }
+
+  public void produce() throws InterruptedException {
+
+    Item item = new Item(name, itemId++);
+    queue.put(item);
+    Random random = new Random();
+    Thread.sleep(random.nextInt(2000));
+  }
+}

producer-consumer/src/test/java/com/iluwatar/poison/pill/AppTest.java

@@ -0,0 +1,20 @@
+package com.iluwatar.poison.pill;
+
+import org.junit.Test;
+
+import com.iluwatar.producer.consumer.App;
+
+/**
+ * 
+ * Application test
+ *
+ */
+public class AppTest {
+
+  @Test
+  public void test() throws Exception {
+    String[] args = {};
+    App.main(args);
+
+  }
+}