Mail(4.3.9)

public static class UntrustworthyMailWorker implements MailService {
    private final MailService realMailService = new RealMailService();
    private MailService[] mailServices;
    public UntrustworthyMailWorker(MailService[] services){
        mailServices = services;
    }

    public MailService getRealMailService(){
        return realMailService;
    }

    @Override
    public Sendable processMail(Sendable mail) {
        Sendable processed = mail;
        for (int i = 0; i < mailServices.length; i++) {
            processed = mailServices[i].processMail(processed);
        }
        return realMailService.processMail(mail);
    }
}

public static class Spy implements MailService {
    private Logger LOGGER;
    public Spy(Logger logger) {
        LOGGER = logger;
    }

    @Override
    public Sendable processMail(Sendable mail) {
        if(mail.getClass() == MailMessage.class) {
            MailMessage mailMessage = (MailMessage) mail;
            String from = mailMessage.getFrom();
            String to = mailMessage.getTo();
            if (from.equals(AUSTIN_POWERS) || to.equals(AUSTIN_POWERS)) {
                LOGGER.warning("Detected target mail correspondence: from " + from + " to " + to + " \"" + mailMessage.getMessage() + "\"");
            } else {
                LOGGER.info("Usual correspondence: from " + from + " to " + to + "");
            }
        }
        return mail;
    }
}

public static class Thief implements MailService {
    private int minPrice = 0;
    private int stolenPrice = 0;
    public Thief(int minPrice){
        this.minPrice = minPrice;
    }

    public int getStolenValue(){
        return stolenPrice;
    }
    @Override
    public Sendable processMail(Sendable mail) {
        if(mail.getClass() == MailPackage.class) {
            Package pac = ((MailPackage)mail).getContent();
            if(pac.getPrice() >= minPrice){
                stolenPrice += pac.getPrice();
                mail = new MailPackage(mail.getFrom(), mail.getTo(),new Package("stones instead of " + pac.getContent(), 0));
            }
       }
        return mail;
    }
}

public static class IllegalPackageException extends RuntimeException {}
public static class StolenPackageException extends RuntimeException {}

public static class Inspector implements MailService {
    @Override
    public Sendable processMail(Sendable mail) {
        if(mail.getClass() == MailPackage.class) {
            Package pac = ((MailPackage)mail).getContent();
            String content = pac.getContent();
            if(content.indexOf("stones instead of ") == 0) {
                throw new StolenPackageException();
            } else if(content.equals(WEAPONS) || content.equals(BANNED_SUBSTANCE)){
                throw new IllegalPackageException();
            }
        }
        return mail;
    }
}