import javax.security.auth.Subject;

public class Main {

    public static void main(String[] args) {
        Subject subject=new Subject();
        subject.getPrivateCredentials().add("alice");
        subject.getPublicCredentials().add("alice 1");

        subject.getPrivateCredentials().add("tom");
        subject.getPublicCredentials().add("tom 1");

        System.out.println(subject.getPrivateCredentials(String.class).iterator().next());
        System.out.println(subject.getPublicCredentials(String.class).iterator().next());
    }
}