Why my Java multithreading code does not work properly?

Question

Really need your help to figure out what is going on. The code seem to be so trivial, but it produces wrong output.

It is a basic producer-consumer problem. Generator thread generates prime numbers and consumer (acceptors) must process them. In App I created two acceptors and 1 generator thread. The problem is that I get the following output for 50 as a bound:

Thread Thread-2 puts 47
Thread Thread-2 puts 43
Thread Rob gets 47
Thread Rob gets 43
Thread Thread-1 gets 47
Thread Nick puts 47
etc...

I have no idea why Thread-2 and Thread-1 are printed... where these threads are coming from? Thanks

public class PrimeGenerator implements Runnable{
    private PrimeCentral primeCentral;
    int bound;

    public PrimeGenerator(PrimeCentral PC, int bound){
        this.primeCentral = PC;
        this.bound = bound;
        new Thread(this).start();
    }

    @Override
    public void run() {
          int n=bound;
          while (n > 1) {
             int d;
             for (d=2; d <= n/2; d++) 
                if ((n % d) == 0) break; 
             if (d > n/2) {
                 primeCentral.put(n);
                System.out.println("Thread " + Thread.currentThread().getName() + " puts " + n);
             }
          n--; 
          }

    }

}

public class PrimeCentral {
    private int prime;
    private boolean available = false;


    public synchronized void put(int n){
        while(available == true){
            try{
                wait();
            }catch(InterruptedException e){}
        }
        prime = n;
        available = true;
        notifyAll();        
    }

    public synchronized int get(){
        while(available == false){
            try{
                wait();
            }catch(InterruptedException e){}
        }
        available = false;
        notifyAll();
        return prime;
    }

}
public class PrimeAcceptor implements Runnable{
    private PrimeCentral primeCentral;

    public PrimeAcceptor(PrimeCentral primeCentral){
        this.primeCentral = primeCentral;
        new Thread(this).start();
    }


    public void run() {
          while (true) {
              int prime = primeCentral.get();
              System.out.println("Thread " + Thread.currentThread().getName() + " gets " + prime);
              if (prime == 2) break; 
          }
    }

public class App {

    public static void main(String[] args) {

        PrimeCentral pc = new PrimeCentral();

        new Thread(new PrimeAcceptor(pc), "Bob").start();
        new Thread(new PrimeAcceptor(pc), "Rob").start();

        new Thread(new PrimeGenerator(pc, 50), "Nick").start();

    }
}

EDIT: sorry people I was dumb with this stupid mistake

Answer 1

You're starting two threads with new Thread(this).start().

They will both have names of the form you mention.

I think you're starting four threads where you only meant to start two. Delete the above line in both places it occurs.