78 lines
2.8 KiB
Java
78 lines
2.8 KiB
Java
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package com.iluwatar.lockableobject;
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import com.iluwatar.lockableobject.domain.Creature;
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import com.iluwatar.lockableobject.domain.Elf;
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import com.iluwatar.lockableobject.domain.Feind;
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import com.iluwatar.lockableobject.domain.Human;
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import com.iluwatar.lockableobject.domain.Orc;
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import java.util.ArrayList;
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import java.util.List;
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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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import lombok.extern.slf4j.Slf4j;
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/**
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* The Lockable Object pattern is a concurrency pattern. Instead of using the "synchronized" word
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* upon the methods to be synchronized, the object which implements the Lockable interface handles
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* the request.
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*
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* <p>In this example, we create a new Lockable object with the SwordOfAragorn implementation of it.
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* Afterwards we create 6 Creatures with the Elf, Orc and Human implementations and assign them each
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* to a Fiend object and the Sword is the target object. Because there is only one Sword and it uses
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* the Lockable Object pattern, only one creature can hold the sword at a given time. When the sword
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* is locked, any other alive Fiends will try to lock, which will result in a race to lock the
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* sword.
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*
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* @author Noam Greenshtain
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*/
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@Slf4j
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public class App implements Runnable {
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private static final int WAIT_TIME = 3;
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private static final int WORKERS = 2;
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private static final int MULTIPLICATION_FACTOR = 3;
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/**
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* main method.
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*
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* @param args as arguments for the main method.
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*/
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public static void main(String[] args) {
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var app = new App();
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app.run();
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}
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@Override
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public void run() {
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// The target object for this example.
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var sword = new SwordOfAragorn();
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// Creation of creatures.
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List<Creature> creatures = new ArrayList<>();
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for (var i = 0; i < WORKERS; i++) {
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creatures.add(new Elf(String.format("Elf %s", i)));
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creatures.add(new Orc(String.format("Orc %s", i)));
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creatures.add(new Human(String.format("Human %s", i)));
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}
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int totalFiends = WORKERS * MULTIPLICATION_FACTOR;
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ExecutorService service = Executors.newFixedThreadPool(totalFiends);
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// Attach every creature and the sword is a Fiend to fight for the sword.
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for (var i = 0; i < totalFiends; i = i + MULTIPLICATION_FACTOR) {
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service.submit(new Feind(creatures.get(i), sword));
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service.submit(new Feind(creatures.get(i + 1), sword));
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service.submit(new Feind(creatures.get(i + 2), sword));
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}
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// Wait for program to terminate.
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try {
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if (!service.awaitTermination(WAIT_TIME, TimeUnit.SECONDS)) {
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LOGGER.info("The master of the sword is now {}.", sword.getLocker().getName());
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}
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} catch (InterruptedException e) {
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LOGGER.error(e.getMessage());
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Thread.currentThread().interrupt();
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} finally {
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service.shutdown();
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}
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}
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}
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