Whats wrong with the code? Why are threads not interleaving?

Question

class Producer implements Runnable{  //producer job here
    Vector<Integer> sQueue;
    public Producer(Vector<Integer> queue) {
        this.sQueue=queue;
    }
    public void run(){
        int i=0;
        try{
            synchronized(sQueue){
                for(i=0;i<30;i++){
                    if(sQueue.size()<15){
                        System.out.println("Producer producing the item:-"+i);
                        sQueue.add(i);
                        sQueue.notifyAll();
                    }
                    else
                    {   sQueue.notifyAll();
                        sQueue.wait();

                    }
                }
            }
        }
        catch(Exception e){
            e.printStackTrace();
        }
    }

}
class Consumer implements Runnable{
    Vector<Integer> sQueue;
    public Consumer(Vector<Integer> queue) {
        this.sQueue=queue;
    }
    public void run(){
        int i=0;
        try{
            synchronized(sQueue){
                while(true){
                    if(sQueue.size()>0){
                        System.out.println("Consumer is removing the item:-");
                        int item=sQueue.remove(0);
                        System.out.println(item);
                        sQueue.notifyAll();
                        Thread.sleep(1000);
                    }
                    else
                    {
                        sQueue.wait();
                    }
                }
            }
        }
        catch(Exception e){
            e.printStackTrace();
        }
    }
}
public class ProducerConsumerProblem {
    public static void main(String [] arg){
        Vector<Integer> sQueue;
        sQueue = new Vector<>(15);
        Producer p=new Producer(sQueue);
        Consumer c=new Consumer(sQueue);
        Thread producer=new Thread(p);
        Thread consumer=new Thread(c);
        producer.start();
        consumer.start();
    }
}

In the above code, i am trying to simulate producer consumer problem with the help of java multi threading. I am using sQueue as a shared queue which is of integer i dont know what is going wrong , producer thread and consumer thread are not interleaving, here is the output on my machine

----------------------------output------------------------
Producer producing the item:-0
Producer producing the item:-1
Producer producing the item:-2
Producer producing the item:-3
Producer producing the item:-4
Producer producing the item:-5
Producer producing the item:-6
Producer producing the item:-7
Producer producing the item:-8
Producer producing the item:-9
Producer producing the item:-10
Producer producing the item:-11
Producer producing the item:-12
Producer producing the item:-13
Producer producing the item:-14
Consumer is removing the item:-
0
Consumer is removing the item:-
1
Consumer is removing the item:-
2
Consumer is removing the item:-
3
Consumer is removing the item:-
4
Consumer is removing the item:-
5
Consumer is removing the item:-
6
Consumer is removing the item:-
7
Consumer is removing the item:-
8
Consumer is removing the item:-
9
Consumer is removing the item:-
10
Consumer is removing the item:-
11
Consumer is removing the item:-
12
Consumer is removing the item:-
13
Consumer is removing the item:-
14
Producer producing the item:-16
Producer producing the item:-17
Producer producing the item:-18
Producer producing the item:-19
Producer producing the item:-20
Producer producing the item:-21
Producer producing the item:-22
Producer producing the item:-23
Producer producing the item:-24
Producer producing the item:-25
Producer producing the item:-26
Producer producing the item:-27
Producer producing the item:-28
Producer producing the item:-29
Consumer is removing the item:-
16
Consumer is removing the item:-
17
Consumer is removing the item:-
18
Consumer is removing the item:-
19
Consumer is removing the item:-
20
Consumer is removing the item:-
21
Consumer is removing the item:-
22
Consumer is removing the item:-
23
Consumer is removing the item:-
24
Consumer is removing the item:-
25
Consumer is removing the item:-
26
Consumer is removing the item:-
27
Consumer is removing the item:-
28
Consumer is removing the item:-
29

Answer 1

Your methods are synchronized. When the Producer starts, it obtains a lock on the queue, and doesn't let go of it until it completes. When your Consumer starts, it waits until it can obtain the lock. If you want them to interleave, don't synchronize... the synchronized keyword is specifically to prevent interleaving.