package com.csdhsm.concurrent;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.TimeUnit;

class CircularSet{

private int[] array;

private int len;

private int index = 0;

public CircularSet(int size){

array = new int[size];

len = size;

//Initialize to a value not produced

//by the SerialNumberGenerator

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

array[i] = -1;

}

}

public synchronized void add(int i){

array[index] = i;

//Wrap index and write over old elements

index = ++index % len;

}

public synchronized boolean contains(int val){

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

if(array[i] == val){

return true;

}

}

return false;

}

}

public class SerialNumberChecker {

private static final int SIZE = 10;

private static CircularSet set = new CircularSet(1000);

private static ExecutorService service = Executors.newCachedThreadPool();

static class SerialChecker implements Runnable{

@Override

public void run() {

while(true){

int serial = SerialNumberGenerator.nextSerialNumber();

if(set.contains(serial)){

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

System.exit(0);

}

set.add(serial);

}

}

}

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

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

service.execute(new SerialChecker());

}

if(args.length > 0){

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

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

System.exit(0);

}

}

}