Dining Philosophers http://geek.daohoangson.com/2010/03/dining-philosophers.html

Chopstick.java

public class Chopstick {
 int cid, used;
 boolean output;
 
 /*
  * Constructor
  * This chopstick is the chopstick number `cid`
  */
 public Chopstick(int cid) {
  this.used = -1;
  this.cid = cid;
  this.output = false;
 }
 
 /*
  * pick method
  * The Philosopher number `pid` is requesting me
  */
 public synchronized void pick(int pid) {
  // check if nobody is using me
  if (used != -1) {
   // this is not the case, you have to wait
   try {
    wait();
   } catch (InterruptedException e) {
    System.out.println(e);
   }
  }
  
  // okie, your turn
  used = pid;
  if (output) System.out.println("Chopstick #" + (cid + 1) + " is picked by #" + (used + 1));
 }
 
 /*
  * release method
  * The Philosopher finished using me
  */
 public synchronized void release(int pid) {
  if (output) System.out.println("Chopstick #" + (cid + 1) + " is releasded by #" + (used + 1));
  used = -1;
  
  // notify who is waiting
  notify();
 }
}

DiningPhilosophers.java

public class DiningPhilosophers {
 public static void main(String[] args) {
  /*
   * Let's create a table with 5 chopsticks
   * And then assign 5 philosophers to it
   */
  int n = 5;
  Table table = new Table(n);
  for (int i = 0; i < n; i++) {
   new Philosopher(table,i,n);
  }
 }
}

Philosopher.java

public class Philosopher implements Runnable {
 private Table table;
 private int pid;
 private int total;
 private int eat_count;
 private int timeout;
 
 /*
  * Constructor
  * Assign our Philosopher to a `table`
  * He will be the guest number `pid`
  * The total number of guests are `total`
  */
 public Philosopher(Table table, int pid, int total) {
  this.table = table;
  this.pid = pid;
  this.total = total;
  this.eat_count = 0;
  this.timeout = 5000;
  
  new Thread(this, "Philosopher " + pid).start();
 }
 
 /*
  * eat method
  * Everybody has to eat at some point in life
  */
 private void eat() {
  eat_count++;
  System.out.println("Philosopher #" + (pid + 1) + " is eating (#" + eat_count + ").");
  
  try {
   Thread.sleep(timeout);
  } catch (InterruptedException e) {
   System.out.println(e);
  }
 }
 
 /*
  * think method
  * A philosopher should love thinking
  */
 private void think() {
  try {
   Thread.sleep(timeout);
  } catch (InterruptedException e) {
   System.out.println(e);
  }
 }
 
 public void run() {
  while (true) {
   // shortcuts
   Chopstick c1 = table.chopsticks[pid];
   Chopstick c2 = table.chopsticks[(pid + 1) % total];
   
   // pick (or wait) for 2 chopsticks
   c1.pick(pid);
   c2.pick(pid);
   
   // great, let's eat
   eat();
   
   // be fair, release the 2 chopsticks
   c1.release(pid);
   c2.release(pid); 
   
   // hmm, to be or not to be?
   think();
  }
 }
}

Table.java

public class Table {
 public Chopstick chopsticks[];
 
 /*
  * Constructor
  * Create a new table with `n` chopsticks
  */
 public Table(int n) {
  chopsticks = new Chopstick[n];
  for (int i = 0; i < n; i++)
   chopsticks[i] = new Chopstick(i);
 }
}