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/*
* Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
* All rights reserved. Software written by Ian F. Darwin and others.
* $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
*/
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
* Simulate multiple readers
* @version $Id: ReadersWriterDemo.java,v 1.5 2004/04/26 02:35:51 ian Exp $
*/
public class ReadersWriterDemo {
  private static final int NUM_READER_THREADS = 3;
  public static void main(String[] args) {
    new ReadersWriterDemo().demo();
  }

  /** Set this to true to end the program */
  private boolean done = false;

  /** The data being protected. */
  private BallotBox theData;

  /** The read lock / write lock combination */
  private ReentrantReadWriteLock lock = new ReentrantReadWriteLock();

  /**
   * Constructor: set up some quasi-random initial data
   */
  public ReadersWriterDemo() {
    List questionsList = new ArrayList();
    questionsList.add("Agree");
    questionsList.add("Disagree");
    theData = new BallotBox(questionsList);
  }

  /**
   * Run a demo with more readers than writers
   */
  private void demo() {

    // Start two reader threads
    for (int i = 0; i < NUM_READER_THREADS; i++) {
      new Thread() {
        public void run() {
          while(!done) {
            Iterator results = null;
            try {
              lock.readLock().lock();
              results = theData.iterator();
            } finally {
              // Unlock in finally to be sure.
              lock.readLock().unlock();
            }
            // Now lock has been freed, take time to print
            print(results);
            try {
              Thread.sleep(((long)(Math.random()* 1000)));
            } catch (InterruptedException ex) {
              // nothing to do
            }
          }
        }
      }.start();
    }
    // Start one writer thread to simulate occasional voting
    new Thread() {
      public void run() {
        while(!done) {
          try {
            lock.writeLock().lock();
            theData.voteFor(
                (((int)(Math.random()*
                theData.getCandidateCount()))));
          } finally {
            lock.writeLock().unlock();
          }
          try {
            Thread.sleep(((long)(Math.random()*1500)));
          } catch (InterruptedException ex) {
            // nothing to do
          }
        }
      }
    }.start();

    // In the main thread, wait a while then terminate the run.
    try {
      Thread.sleep(10 *1000);
    } catch (InterruptedException ex) {
      // nothing to do
    } finally {
      done = true;
    }
  }

  /** print the current totals */
  private void print(Iterator iter) {
    boolean first = true;
    while (iter.hasNext()) {
      BallotPosition pair = (BallotPosition) iter.next();
      if (!first)
        System.out.print(", ");
      System.out.print(pair.getName() + "(" + pair.getVotes() + ")");
      first = false;
    }
    System.out.println();
  }

}

/**
* Java Code from Java Cookbook, Second Edition
* By Ian F. Darwin
* Second Edition June 2004
* Series: Cookbooks
* ISBN: 0-596-00701-9
* Details: http://www.oreilly.com/catalog/javacook2/index.html
* Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
* All rights reserved. Software written by Ian F. Darwin and others.
* $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
*/