Train simulator - Threading

[bangor_boy]

Hi, Trying to get this bit of code to work so that a train goes up the track, leaves the track and then a train comes down the track, leaves and then a train comes up the track and so on. Only one train is allowed to go onto the track at anytime. My output starts off as this
Train 1 entered track, going DOWN
Train 1 left track, going DOWN
Train 7 entered track, going UP
Train 7 left track, going UP
Train 3 entered track, going DOWN
Train 3 left track, going DOWN
Train 6 entered track, going UP
Train 6 left track, going UP

which is right but then turns too

Train 8 left track, going UP
Train 5 left track, going UP
Train 4 left track, going DOWN
Train 2 left track, going DOWN

I have no idea why this is happening and if someone could show me where i have went wrong and why its went wrong i would be greatful.

public class UpDownTrack extends OpenTrack
{
    //Add the allowedDirection attribute required
    private TrainDirection allowedDir;
   
    //Add a constructor to set the initial state of an UpDOwnTrack
    public UpDownTrack()
    {
        allowedDir = DOWN;
    }
    
    // only allows one train on the track
    public synchronized void useTrack(TrainDirection trainDir, int id)
    {
       
       try
       {
         enterTrack(trainDir,  id);
         traverse();
         exitTrack(trainDir,id);
       }
       catch(Exception e)
       {
         System.out.println("Error" + e);  
       }
       
                
    } 
    
    // Only allows a train to leave in the opposite direction
    public synchronized void enterTrack(TrainDirection trainDir, int id)
    {
       if(allowedDir != trainDir)
       {
         try
         { 
           wait();
         }
         catch (Exception e)
         {
            System.out.println(e);
         }
       }
       else
       {
           System.out.println("Train " + id + " entered track, going " + trainDir);
       }
     
    }
    
    // Tells us train has left the track and changes the direction
    public synchronized void exitTrack(TrainDirection trainDir, int id)
    {      
        
        System.out.println("   Train " + id + " left track, going " + trainDir);
        allowedDir = (allowedDir == DOWN)? UP : DOWN;
        notifyAll();
    }
    
    
    public boolean unsafeToEnter(TrainDirection trainDir)
    {
        return false; //always safe!?
    }  
    
    
}

Thanks

[NormR1]

Could you post a version of your code that will compile and execute and demo your problem?