package concurrency;

import java.util.concurrent.*;

import java.util.concurrent.locks.*;

/**

* RUN:

* javac concurrency/SerialNumberChecker.java && java concurrency.SerialNumberChecker

*

* OUTPUT:

*

*/

public class SerialNumberChecker {

private static final int SIZE = 10;

private static CircularSet serials = new CircularSet(1000);

private static ExecutorService exec = Executors.newCachedThreadPool();

static class SerialChecker implements Runnable {

public void run() {

while (true) {

int serial = SerialNumberGenerator.nextSerialNumber();

if (serials.contains(serial)) {

System.out.println("Duplicate: "+serial);

System.exit(0);

}

serials.add(serial);

}

}

}

public static void main(String[] args) throws Exception {

for (int i = 0; i < SIZE; i++) {

exec.execute(new SerialChecker());

}

if (args.length > 0) {

TimeUnit.SECONDS.sleep(new Integer(args[0]));

System.out.println("No duplicates detected");

System.exit(0);

}

}

}

class CircularSet {

private int[] array;

private int len;

private int index = 0;

public CircularSet(int size) {

array = new int[size];

len = size;

for (int i = 0; i < size; i++) {

array[i] = -1;

}

}

public synchronized void add(int i) {

array[index] = i;

index = ++index % len;

}

public synchronized boolean contains(int val) {

for (int i = 0; i < len; i++) {

if (array[i] == val) {

return true;

}

}

return false;

}

}