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Я разрабатываю симуляцию аэропорта и столкнулся с трудностями. Я пытаюсь спроектировать, когда самолеты получили доступ к 4 воротам, поток ATC отобразит вывод о том, что ворота заполнены (например: ворот не осталось). Так или иначе, в моем выводе есть ошибка…

 import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.ArrayDeque;
import java.util.Arrays;
import java.util.Deque;
import java.util.OptionalInt;
import java.util.Random;

public class Main {

    public static void main(String[] args) {
        // TODO code application logic here
        Runway runway= new Runway();
        
        for(int i=1 ; i<= 10 ; i  )
        {
            Plane p = new Plane(i, runway);
            p.start();
        }
        
        ATC atc= new ATC(runway);
        atc.start();
    }
}

public class Plane extends Thread{
    Runway runway;
    int id;
    
    Plane(int id, Runway runway)
    {
        this.id = id;
        this.runway = runway;
    }
    
    @Override
    public void run()
    {
        try {
            runway.required_to_land(this);
            
        } catch (InterruptedException ex) {
            Logger.getLogger(Plane.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

public class ATC extends Thread{
    
    Runway runway;

    public ATC(Runway runway)
    {
        this.runway= runway;
    }
    
    @Override
    public void run()
    {
        try {
            Thread.sleep(1000);
        } catch (InterruptedException ex) {
            Logger.getLogger(ATC.class.getName()).log(Level.SEVERE, null, ex);
        }
          
        while(!runway.maybeGateNumber.isPresent())
            {
                System.out.println("ATC: There is no gates left!");
            }
        
        
    }
}

public class Runway {
    
    final Deque<Integer> availableGates = new ArrayDeque<>(Arrays.asList(1, 2, 3, 4));
    
    OptionalInt claimGate() {
        synchronized (availableGates) {
        if (availableGates.isEmpty()) {
            // You need to handle the possibility of no gates.
                return OptionalInt.empty();
        }
        return OptionalInt.of(availableGates.removeFirst());
        }
    }
    
    void releaseGate(int gateNumber) {
        synchronized (availableGates) {
            availableGates.add(gateNumber);
        }
    }
    
    void required_to_land(Plane plane) throws InterruptedException
    {
        Thread.sleep(new Random().nextInt(3000));
        System.out.println("Plane "  plane.id   " requests to land!");
        
        Thread.sleep(500);
        
        access_runway(plane);
    }
    
    OptionalInt maybeGateNumber;
    
    void access_runway(Plane plane) throws InterruptedException
    {
        int gateNumber;
        
        synchronized(this){
            
        maybeGateNumber = claimGate();
            
        System.out.println("Plane "   plane.id   " is accessing the runway!");
        Thread.sleep(1000);
        gateNumber = maybeGateNumber.getAsInt();
        System.out.println("Plane "   plane.id  " has landed at gate "   gateNumber   "!");
        }
        access_gate(plane, gateNumber);
    }
    
    void access_gate(Plane plane, int gateNumber) throws InterruptedException
    {
        Thread.sleep(new Random().nextInt(8000));
        System.out.println("Plane "   plane.id  " had left gate "   gateNumber   "!");
        releaseGate(gateNumber);
    }
}
 

Ниже приведен мой результат!

 Plane 2 requests to land!
Plane 6 requests to land!
Plane 2 is accessing the runway!
Plane 8 requests to land!
Plane 1 requests to land!
Plane 2 has landed at gate 1!
Plane 8 is accessing the runway!
Plane 4 requests to land!
Plane 3 requests to land!
Plane 7 requests to land!
Plane 8 has landed at gate 2!
Plane 6 is accessing the runway!
Plane 5 requests to land!
Plane 10 requests to land!
Plane 9 requests to land!
Plane 6 has landed at gate 3!
Plane 9 is accessing the runway!
Plane 9 has landed at gate 4!
Plane 10 is accessing the runway!
Plane 5 is accessing the runway!
Exception in thread "Thread-9" java.util.NoSuchElementException: No value present
    at java.util.OptionalInt.getAsInt(OptionalInt.java:118)
    at assignment_self.Runway.access_runway(Runway.java:62)
    at assignment_self.Runway.required_to_land(Runway.java:41)
    at assignment_self.Plane.run(Plane.java:21)
Plane 7 is accessing the runway!
Exception in thread "Thread-4" java.util.NoSuchElementException: No value present
    at java.util.OptionalInt.getAsInt(OptionalInt.java:118)
    at assignment_self.Runway.access_runway(Runway.java:62)
    at assignment_self.Runway.required_to_land(Runway.java:41)
    at assignment_self.Plane.run(Plane.java:21)
Plane 8 had left gate 2!
Plane 3 is accessing the runway!
Exception in thread "Thread-6" java.util.NoSuchElementException: No value present
    at java.util.OptionalInt.getAsInt(OptionalInt.java:118)
    at assignment_self.Runway.access_runway(Runway.java:62)
    at assignment_self.Runway.required_to_land(Runway.java:41)
    at assignment_self.Plane.run(Plane.java:21)
Plane 6 had left gate 3!
Plane 3 has landed at gate 2!
Plane 4 is accessing the runway!
Plane 2 had left gate 1!
Plane 9 had left gate 4!
Plane 4 has landed at gate 3!
Plane 1 is accessing the runway!
Plane 1 has landed at gate 1!
Plane 4 had left gate 3!
Plane 1 had left gate 1!
Plane 3 had left gate 2!
 

Было бы здорово, если бы кто — нибудь смог мне помочь! Заранее благодарю вас!