java - why consumer thread is starting first?

Question

package ProducerConsumer;

public class Queue {

    int item;
    boolean isEmpty=false;

    public int put(int item)
    {
        this.item=item;
        return this.item;
    }

    public int get()
    {
        return item;
    }

}

package ProducerConsumer;

public class Producer extends Thread{


    Queue q;
    public Producer(Queue q)
    {
        this.q=q;
    }

    @Override
    public void run() {

        synchronized (q) {

            for(int i=1;i<=5;i++)
            {
                if(q.isEmpty==false)
                    try {
                        q.wait();
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                System.out.println("Producer produced = "+q.put(i));
                q.isEmpty=false;
                q.notify();
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }


        }
    }

}

package ProducerConsumer;

public class Consumer extends Thread {

    Queue q;
    public Consumer(Queue q)
    {
        this.q=q;
    }

    @Override
    public void run() {
        // TODO Auto-generated method stub
        synchronized (q) {
            for(int i=1;i<=5;i++)
            {
                if(q.isEmpty==true)
                    try {
                        q.wait();
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }

                    System.out.println("ITEM CONSUMED:"+q.get());
                    q.isEmpty=true;
                    q.notify();

            }
        }
    }

}

package ProducerConsumer;

public class MainApp {
    public static void main(String[] args)

    {
        Queue q=new Queue();

        Thread t1=new Thread(new Producer(q));
                //t1.setPriority(1);
        t1.start();

        Thread t2=new Thread(new Consumer(q));
        t2.start();



    }
}

This is my output:

ITEM CONSUMED:0
Producer produced = 1
ITEM CONSUMED:1
Producer produced = 2
ITEM CONSUMED:2
Producer produced = 3
ITEM CONSUMED:3
Producer produced = 4
ITEM CONSUMED:4
Producer produced = 5

Question is: why my consumer thread is running first ? I tried setting the priority for my Producer thread also. Its not working. Also, if there is any other flaw in the code or design flaw in code, please do mention.

Answer 1

synchronized (q) {

You told all of your threads to never run at the same time.
That defeats the purpose of threads.

Answer 2

线程的并行执行意味着它们可以以任何顺序运行。如果您希望它们以预定义的顺序运行，则必须明确编程。线程的启动顺序并不是设置线程执行顺序的意思。