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marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

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public interface Observer {
    void notify(String message);
}

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public interface Observable {
    void addObserver(Observer observer);
    void removeObserver(Observer observer);
    void notifyObserver();
}

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import java.util.ArrayList;
import java.util.List;

public class NoticeObservable implements Observable {

    private List<Observer> observerList = new ArrayList<>();
    private String message = "Notice... !";

    @Override
    public void addObserver(Observer observer) {

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public class UserMan implements Observer {

    private Observable observable;

    @Override
    public void notify(String message) {
        System.out.println(message + " UserMan Mesaj Geldi.");
    }

    public void removeObserver(){

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public class UserWoman implements Observer {

    private Observable observable;

    public UserWoman() {
    }

    public void setObservable(Observable observable) {
        this.observable = observable;
    }

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public class Main {

    public static void main(String[] args) {

        UserMan userMan = new UserMan();
        UserWoman userWoman = new UserWoman();

        NoticeObservable noticeObservable = new NoticeObservable();

        userWoman.setObservable(noticeObservable);

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public interface Computer {
    void name();
    void since(int year);
}

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public class Mac implements Computer {

    @Override
    public void name() {
        System.out.println("Bilgisayarın Markası Mac");
    }

    @Override
    public void since(int year) {
        System.out.println(year + " senesinde alınmış.");

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public class Asus implements Computer {

    @Override
    public void name() {
        System.out.println("Bilgisayarın Markası Asus");
    }

    @Override
    public void since(int year) {
        System.out.println(year + " senesinde alınmış.");