/***
 * Excerpted from "Programming Concurrency on the JVM",
 * published by The Pragmatic Bookshelf.
 * Copyrights apply to this code. It may not be used to create training material, 
 * courses, books, articles, and the like. Contact us if you are in doubt.
 * We make no guarantees that this code is fit for any purpose. 
 * Visit http://www.pragmaticprogrammer.com/titles/vspcon for more book information.
***/
package com.agiledeveloper.pcj;

import java.util.List;
import java.util.ArrayList;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Callable;
import java.util.concurrent.Future;
import java.util.concurrent.ExecutionException;

public class UseEnergySource {
  private static final EnergySource energySource = EnergySource.create();
    
  public static void main(final String[] args) 
    throws InterruptedException, ExecutionException {
    System.out.println("Energy level at start: " + 
      energySource.getUnitsAvailable());
        
    List<Callable<Object>> tasks = new ArrayList<Callable<Object>>();    

    for(int i = 0; i < 10; i++) {
      tasks.add(new Callable<Object>() {
        public Object call() {
          for(int j = 0; j < 7; j++) energySource.useEnergy(1);
          return null;
        }
      });
    }
    
    final ExecutorService service = Executors.newFixedThreadPool(10);
    service.invokeAll(tasks);
    
    System.out.println("Energy level at end: " + 
      energySource.getUnitsAvailable());
    System.out.println("Usage: " + energySource.getUsageCount());
    
    energySource.stopEnergySource();
    service.shutdown();
  }
}