Tickets

Program

/*
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 */
package tickets;

/**
 *
 * @author mikhail
 */
public class Program {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        TicketMachine tm = new TicketMachine();
        TicketMachine tm2 = new TicketMachine();
        
        //tm.buyTicket("Sherlock");
        //tm2.buyTicket("HALK");
        Ticket t1 = tm.buyTicket("Sherlock");
        Ticket t3 = tm.buyTicket("Alala");
        Ticket t2 = tm2.buyTicket("HALK");
        Ticket t4 = tm2.buyTicket("Madagaskar");
        
        System.out.println(t1);
        System.out.println(tm.isValid(t1));
        
        tm.useTicket(t1);
        
        System.out.println(tm.isValid(t1));
        
    }

}

Ticket

/*
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 * To change this template file, choose Tools | Templates
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 */
package tickets;

import java.util.Objects;

/**
 *
 * @author mikhail
 */
public class Ticket {

    private static int nextNumber = 1001;
    private String movie;
    private int serialNumber;

    public Ticket(String movie) {
        this.movie = movie;
        serialNumber = nextNumber++;
    }

    @Override
    public String toString() {
        return String.format("#%d %10s", serialNumber, movie);
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }
        if (!(obj instanceof Ticket)) {
            return false;
        }
        Ticket some = (Ticket) obj;
        return movie.equals(some.movie) && serialNumber == some.serialNumber;
    }

    @Override
    public int hashCode() {
        int hash = 5;
        hash = 47 * hash + Objects.hashCode(this.movie);
        hash = 47 * hash + this.serialNumber;
        return hash;
    }

}

TicketMachine

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package tickets;

/**
 *
 * @author mikhail
 */
import java.util.*;

public class TicketMachine {

    private static ArrayList<Ticket> legalTickets = new ArrayList<Ticket>();

    public Ticket buyTicket(String movie) {
        Ticket ticket = new Ticket(movie);
        legalTickets.add(ticket);
        return ticket;
    }
    
    public boolean isValid(Ticket ticket){
        return legalTickets.contains(ticket);
    }
    
    public boolean useTicket(Ticket ticket){
        if(!isValid(ticket)){
            return false;
        }
        legalTickets.remove(ticket);
        return true;
    }
}