import java.util.concurrent.*;
import  java.util.concurrent.atomic.*;

public class Elevator{
    private int floor;
    int current_floor=0;
    AtomicBoolean busy= new AtomicBoolean(false);

    Elevator(int num_floor){
        floor= 0;
    }

    public void call(int floor){
        new Thread(){
            public void run(){
                synchronized(busy){
                    while(busy.get()){
                        try{
                            System.out.println("Call in wait");
                            busy.wait();
                        }
                        catch(InterruptedException ex){}
                        move(floor);
                    }
                    move(floor);
                }
            }
        }.start();
    }

    public void move(int floor){
        synchronized(busy){
            while(busy.get()){
                try{
                    busy.wait();
                }
                catch(InterruptedException ex){}
            }
            try{
                busy.set(true);
                System.out.println("Leaving floor "+ current_floor);
                Thread.currentThread().sleep(2000);
                current_floor=floor;
                System.out.println("Reaching floor "+ current_floor);
                busy.set(false);
                busy.notify();
            }
            catch(InterruptedException ex){}
        }
    }

    public static void main(String args[]){
        Elevator e= new Elevator(10);
        e.call(1);
        e.call(2);
    }
}