import java.util.*;
import java.util.concurrent.*;

class LanesAndBoxesAnswer {
  public static void main(String[] args) {
     BlockingQueue<Box> lane1 = new LinkedBlockingQueue<Box>();
     BlockingQueue<Box> lane2 = new LinkedBlockingQueue<Box>();
     BlockingQueue<Box> lane3 = new LinkedBlockingQueue<Box>();
     Map<Integer, BlockingQueue<Box>> lanes = new ConcurrentHashMap<Integer, BlockingQueue<Box>>();
     lanes.put(1, lane1);
     lanes.put(2, lane2);
     lanes.put(3, lane3);

     Producer p = new Producer(lanes);
     Consumer c1 = new Consumer(1, lane1);
     Consumer c2 = new Consumer(2, lane2);
     Consumer c3 = new Consumer(3, lane3);

     new Thread(p).start();
     new Thread(c1).start();
     new Thread(c2).start();
     new Thread(c3).start();
  }
}

class Box {
  private final int groupId;
  public Box(int groupId) {
    this.groupId = groupId;
  }
  @Override
  public String toString() {
    return "<Box " + groupId + ">";
  }
}

class Producer implements Runnable {
   private final Map<Integer, BlockingQueue<Box>> lanes;
   Producer(Map<Integer, BlockingQueue<Box>> lanes) {
     this.lanes = lanes;
   }
   public void run() {
     try {
       while (true) {
         int groupId = produceGroupId();
         BlockingQueue<Box> lane = lanes.get(groupId);
         lane.put(new Box(groupId));
       }
     } catch (InterruptedException ex) {
       Thread.currentThread().interrupt();
     }
   }
   int produceGroupId() {
     // generate random int between 1 and 3
     return ThreadLocalRandom.current().nextInt(1, 4);
   }
}

class Consumer implements Runnable {
   private final int consumerId;
   private final BlockingQueue<Box> lane;
   Consumer(int consumerId, BlockingQueue<Box> lane) {
     this.consumerId = consumerId;
     this.lane = lane;
   }
   public void run() {
     try {
       while (true) {
         consume(lane.take());
       }
     } catch (InterruptedException ex) {}
   }
   void consume(Box box) {
     System.out.println("Consumer " + consumerId + " received " + box + " for proxessing.");
   }
}