JavaRush /Java Blog /Random-TL /Mga Pattern ng Disenyo sa Java [Bahagi 2]

Antas

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28 February 2021
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Mga Pattern ng Disenyo sa Java [Bahagi 2]

Kamusta kayong lahat. Sa aking lumang paksa, maikli kong inilarawan ang bawat pattern, sa paksang ito susubukan kong ipakita nang detalyado kung paano gamitin ang mga pattern.

Generative

Singleton

Paglalarawan :

Nililimitahan ang paglikha ng isang instance ng isang klase at nagbibigay ng access sa nag-iisang object nito. Ang tagabuo ng klase ay pribado. Ang pamamaraan getInstance()ay lumilikha lamang ng isang halimbawa ng klase.

Pagpapatupad:

class Singleton {
    private static Singleton instance = null;
    private Singleton() {}
    public static Singleton getInstance() {
        if (instance == null) {
            instance = new Singleton();
		}
        return instance;
    }
    public void setUp() {
        System.out.println("setUp");
    }
}

public class SingletonTest {//тест
    public static void main(String[] args){
        Singleton singelton = Singleton.getInstance();
        singelton.setUp();
    }
}

Pabrika

Paglalarawan :

Ginagamit kapag mayroon tayong super class na may maraming subclass at batay sa input na kailangan nating ibalik ang isa mula sa subclass. Hindi alam ng klase kung anong uri ng bagay ang dapat nitong gawin. Ang mga bagay ay nilikha depende sa papasok na data.

Pagpapatupad:

class Factory {
    public OS getCurrentOS(String inputos) {
        OS os = null;
        if (inputos.equals("windows")) {
            os = new windowsOS();
        } else if (inputos.equals("linux")) {
            os = new linuxOS();
        } else if (inputos.equals("mac")) {
            os = new macOS();
        }
        return os;
    }
}
interface OS {
    void getOS();
}
class windowsOS implements OS {
    public void getOS () {
        System.out.println("применить для виндовс");
    }
}
class linuxOS implements OS {
    public void getOS () {
        System.out.println("применить для линукс");
    }
}
class macOS implements OS {
    public void getOS () {
        System.out.println("применить для мак");
    }
}

public class FactoryTest {//тест
    public static void main(String[] args){
        String win = "linux";
        Factory factory = new Factory();
        OS os = factory.getCurrentOS(win);
        os.getOS();
    }
}

Abstract na Pabrika

Paglalarawan :

Binibigyang-daan kang pumili ng partikular na pagpapatupad ng pabrika mula sa isang pamilya ng mga posibleng pabrika. Lumilikha ng isang pamilya ng mga kaugnay na bagay. Madaling palawakin.

Pagpapatupad:

interface Lada {
    long getLadaPrice();
}
interface Ferrari {
    long getFerrariPrice();
}
interface Porshe {
    long getPorshePrice();
}
interface InteAbsFactory {
    Lada getLada();
    Ferrari getFerrari();
    Porshe getPorshe();
}
class UaLadaImpl implements Lada {// первая
    public long getLadaPrice() {
        return 1000;
    }
}
class UaFerrariImpl implements Ferrari {
    public long getFerrariPrice() {
        return 3000;
    }
}
class UaPorsheImpl implements Porshe {
    public long getPorshePrice() {
        return 2000;
    }
}
class UaCarPriceAbsFactory implements InteAbsFactory {
    public Lada getLada() {
        return new UaLadaImpl();
    }
    public Ferrari getFerrari() {
        return new UaFerrariImpl();
    }
    public Porshe getPorshe() {
        return new UaPorsheImpl();
    }
}// первая
class RuLadaImpl implements Lada {// вторая
    public long getLadaPrice() {
        return 10000;
    }
}
class RuFerrariImpl implements Ferrari {
    public long getFerrariPrice() {
        return 30000;
    }
}
class RuPorsheImpl implements Porshe {
    public long getPorshePrice() {
        return 20000;
    }
}
class RuCarPriceAbsFactory implements InteAbsFactory {
    public Lada getLada() {
        return new RuLadaImpl();
    }
    public Ferrari getFerrari() {
        return new RuFerrariImpl();
    }
    public Porshe getPorshe() {
        return new RuPorsheImpl();
    }
}// вторая

public class AbstractFactoryTest {//тест
    public static void main(String[] args) {
        String country = "UA";
        InteAbsFactory ifactory = null;
        if(country.equals("UA")) {
            ifactory = new UaCarPriceAbsFactory();
        } else if(country.equals("RU")) {
            ifactory = new RuCarPriceAbsFactory();
        }

        Lada lada = ifactory.getLada();
        System.out.println(lada.getLadaPrice());
    }
}

Tagabuo

Paglalarawan :

Ginagamit upang lumikha ng isang kumplikadong bagay gamit ang mga simpleng bagay. Unti-unti itong lumilikha ng mas malaking bagay mula sa isang maliit at simpleng bagay. Binibigyang-daan kang baguhin ang panloob na representasyon ng panghuling produkto.

Pagpapatupad:

class Car {
    public void buildBase() {
        print("Doing корпус");
    }
    public void buildWheels() {
        print("Ставим колесо");
    }
    public void buildEngine(Engine engine) {
        print("Ставим движок: " + engine.getEngineType());
    }
    private void print(String msg){
        System.out.println(msg);
    }
}
interface Engine {
    String getEngineType();
}
class OneEngine implements Engine {
    public String getEngineType() {
        return "Первый двигатель";
    }
}
class TwoEngine implements Engine {
    public String getEngineType() {
        return "Второй двигатель";
    }
}
abstract class Builder {
    protected Car car;
    public abstract Car buildCar();
}
class OneBuilderImpl extends Builder {
    public OneBuilderImpl(){
        car = new Car();
    }
    public Car buildCar() {
        car.buildBase();
        car.buildWheels();
        Engine engine = new OneEngine();
        car.buildEngine(engine);
        return car;
    }
}
class TwoBuilderImpl extends Builder {
    public TwoBuilderImpl(){
        car = new Car();
    }
    public Car buildCar() {
        car.buildBase();
        car.buildWheels();
        Engine engine = new OneEngine();
        car.buildEngine(engine);
        car.buildWheels();
        engine = new TwoEngine();
        car.buildEngine(engine);
        return car;
    }
}
class Build {
    private Builder builder;
    public Build(int i){
        if(i == 1) {
            builder = new OneBuilderImpl();
        } else if(i == 2) {
            builder = new TwoBuilderImpl();
        }
    }
    public Car buildCar(){
        return builder.buildCar();
    }
}

public class BuilderTest {//тест
    public static void main(String[] args) {
        Build build = new Build(1);
        build.buildCar();
    }
}

Prototype

Paglalarawan :

Tumutulong na lumikha ng isang duplicate na bagay na may mas mahusay na pagganap, sa halip na lumikha ng bago, isang ibinalik na clone ng umiiral na bagay ay nilikha. Kino-clone ang isang umiiral na bagay.

Pagpapatupad:

interface Copyable {
    Copyable copy();
}
class ComplicatedObject implements Copyable {
    private Type type;
    public enum Type {
        ONE, TWO
    }
    public ComplicatedObject copy() {
        ComplicatedObject complicatedobject = new ComplicatedObject();
        return complicatedobject;
    }
    public void setType(Type type) {
        this.type = type;
    }
}

public class PrototypeTest {//тест
    public static void main(String[] args) {
        ComplicatedObject prototype = new ComplicatedObject();
        ComplicatedObject clone = prototype.copy();
        clone.setType(ComplicatedObject.Type.ONE);
    }
}

Structural

Adapter

Paglalarawan :

Gamit ang isang pattern, maaari nating pagsamahin ang dalawang bagay na hindi magkatugma. Converter sa pagitan ng dalawang bagay na hindi magkatugma.

Pagpapatupad:

class PBank {
	private int balance;
	public PBank() { balance = 100; }
	public void getBalance() {
		System.out.println("PBank balance = " + balance);
	}
}
class ABank {
	private int balance;
	public ABank() { balance = 200; }
	public void getBalance() {
		System.out.println("ABank balance = " + balance);
	}
}
class PBankAdapter extends PBank {
	private ABank abank;
	public PBankAdapter(ABank abank) {
		this.abank = abank;
	}
	public void getBalance() {
		abank.getBalance();
	}
}

public class AdapterTest {//тест
	public static void main(String[] args) {
		PBank pbank = new PBank();
		pbank.getBalance();
		PBankAdapter abank = new PBankAdapter(new ABank());
		abank.getBalance();
	}
}

Composite

Paglalarawan :

Nagpangkat ng maraming bagay sa isang istraktura ng puno gamit ang isang klase. Binibigyang-daan kang magtrabaho kasama ang ilang mga klase sa pamamagitan ng isang bagay.

Pagpapatupad:

import java.util.ArrayList;
import java.util.List;
interface Car {
    void draw(String color);
}
class SportCar implements Car {
    public void draw(String color) {
        System.out.println("SportCar color: " + color);
    }
}
class UnknownCar implements Car {
    public void draw(String color) {
        System.out.println("UnknownCar color: " + color);
    }
}
class Drawing implements Car {
    private List<Car> cars = new ArrayList<Car>();
    public void draw(String color) {
        for(Car car : cars) {
            car.draw(color);
        }
    }
    public void add(Car s){
        this.cars.add(s);
    }
    public void clear(){
		System.out.println();
        this.cars.clear();
    }
}

public class CompositeTest {//тест
    public static void main(String[] args) {
        Car sportCar = new SportCar();
        Car unknownCar = new UnknownCar();
        Drawing drawing = new Drawing();
        drawing.add(sportCar);
        drawing.add(unknownCar);
        drawing.draw("green");
        drawing.clear();
        drawing.add(sportCar);
        drawing.add(unknownCar);
        drawing.draw("white");
    }
}

Proxy

Paglalarawan :

Kinakatawan ang mga bagay na maaaring kontrolin ang iba pang mga bagay sa pamamagitan ng pagharang sa kanilang mga tawag. Posibleng harangin ang tawag sa orihinal na bagay.

Pagpapatupad:

interface Image {
    void display();
}
class RealImage implements Image {
    private String file;
    public RealImage(String file){
        this.file = file;
        load(file);
    }
    private void load(String file){
        System.out.println("Загрузка " + file);
    }
    public void display() {
        System.out.println("Просмотр " + file);
    }
}
class ProxyImage implements Image {
    private String file;
    private RealImage image;
    public ProxyImage(String file){
        this.file = file;
    }
    public void display() {
        if(image == null){
            image = new RealImage(file);
        }
        image.display();
    }
}

public class ProxyTest {//тест
    public static void main(String[] args) {
        Image image = new ProxyImage("test.jpg");
        image.display();
        image.display();
    }
}

Flyweight

Paglalarawan :

Sa halip na lumikha ng isang malaking bilang ng mga katulad na bagay, ang mga bagay ay muling ginagamit. Nagse-save ng memorya.

Pagpapatupad:

class Flyweight {
    private int row;
    public Flyweight(int row) {
        this.row = row;
        System.out.println("ctor: " + this.row);
    }
    void report(int col) {
        System.out.print(" " + row + col);
    }
}

class Factory {
    private Flyweight[] pool;
    public Factory(int maxRows) {
        pool = new Flyweight[maxRows];
    }
    public Flyweight getFlyweight(int row) {
        if (pool[row] == null) {
            pool[row] = new Flyweight(row);
        }
        return pool[row];
    }
}

public class FlyweightTest {//тест
    public static void main(String[] args) {
        int rows = 5;
        Factory theFactory = new Factory(rows);
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < rows; j++) {
                theFactory.getFlyweight(i).report(j);
            }
            System.out.println();
        }
    }
}

Facade

Paglalarawan :

Itinatago ang isang kumplikadong sistema ng klase sa pamamagitan ng pag-cast ng lahat ng tawag sa isang bagay. Naglalagay ng isang tawag sa maraming kumplikadong mga bagay sa isang solong bagay.

Pagpapatupad:

interface Car {
    void start();
    void stop();
}
class Key implements Car {
    public void start() {
        System.out.println("Вставить ключи");
    }
    public void stop() {
        System.out.println("Вытянуть ключи");
    }
}
class Engine implements Car {
    public void start() {
        System.out.println("Запустить двигатель");
    }
    public void stop() {
        System.out.println("Остановить двигатель");
    }
}
class Facade {
    private Key key;
    private Engine engine;
    public Facade() {
        key = new Key();
        engine = new Engine();
    }
    public void startCar() {
        key.start();
        engine.start();
    }
    public void stoptCar() {
        key.stop();
        engine.stop();
    }
}

public class FacadeTest {//тест
    public static void main(String[] args) {
        Facade facade = new Facade();
        facade.startCar();
        System.out.println();
        facade.stoptCar();
    }
}

tulay

Paglalarawan :

Pinaghihiwalay ang pagpapatupad at abstraction, na ginagawang posible na malayang baguhin ang mga ito mula sa isa't isa. Ginagawang hiwalay ang mga kongkretong klase sa mga klase sa pagpapatupad ng interface.

Pagpapatupad:

interface Engine {
    void setEngine();
}
abstract class Car {
    protected Engine engine;
    public Car(Engine engine){
        this.engine = engine;
    }
    abstract public void setEngine();
}
class SportCar extends Car {
    public SportCar(Engine engine) {
        super(engine);
    }
    public void setEngine() {
        System.out.print("SportCar engine: ");
        engine.setEngine();
    }
}
class UnknownCar extends Car {
    public UnknownCar(Engine engine) {
        super(engine);
    }
    public void setEngine() {
        System.out.print("UnknownCar engine: ");
        engine.setEngine();
    }
}
class SportEngine implements Engine {
    public void setEngine(){
        System.out.println("sport");
    }
}
class UnknownEngine implements Engine {
    public void setEngine(){
        System.out.println("unknown");
    }
}
public class BridgeTest {//тест
    public static void main(String[] args) {
        Car sportCar = new SportCar(new SportEngine());
        sportCar.setEngine();
        System.out.println();
        Car unknownCar = new UnknownCar(new UnknownEngine());
        unknownCar.setEngine();
    }
}

Dekorador

Paglalarawan :

Nagdaragdag ng bagong pag-andar sa isang umiiral na bagay nang hindi nagbubuklod sa istraktura nito.

Pagpapatupad:

interface Car {
    void draw();
}
class SportCar implements Car {
    public void draw() {
        System.out.println("SportCar");
    }
}
class UnknownCar implements Car {
    public void draw() {
        System.out.println("UnknownCar");
    }
}
abstract class CarDecorator implements Car {
    protected Car decorated;
    public CarDecorator(Car decorated){
        this.decorated = decorated;
    }
    public void draw(){
        decorated.draw();
    }
}
class BlueCarDecorator extends CarDecorator {
    public BlueCarDecorator(Car decorated) {
        super(decorated);
    }
    public void draw() {
        decorated.draw();
        setColor();
    }
    private void setColor(){
        System.out.println("Color: red");
    }
}

public class DecoratorTest {//тест
    public static void main(String[] args) {
        Car sportCar = new SportCar();
        Car blueUnknownCar = new BlueCarDecorator(new UnknownCar());
        sportCar.draw();
        System.out.println();
        blueUnknownCar.draw();
    }
}

Pag-uugali

Paraan ng Template

Paglalarawan :

Binibigyang-daan kang tukuyin ang batayan ng isang algorithm at pinapayagan ang mga subclass na i-override ang ilang mga hakbang ng algorithm nang hindi binabago ang pangkalahatang istraktura nito.

Pagpapatupad:

abstract class Car {
    abstract void startEngine();
    abstract void stopEngine();

    public final void start(){
        startEngine();
        stopEngine();
    }
}
class OneCar extends Car {
    public void startEngine() {
        System.out.println("Start engine.");
    }
    public void stopEngine() {
        System.out.println("Stop engine.");
    }
}
class TwoCar extends Car {
    public void startEngine() {
        System.out.println("Start engine.");
    }
    public void stopEngine() {
        System.out.println("Stop engine.");
    }
}

public class TemplateTest {//тест
    public static void main(String[] args) {
        Car car1 = new OneCar();
        car1.start();
        System.out.println();
        Car car2 = new TwoCar();
        car2.start();
    }
}

Tagapamagitan

Paglalarawan :

Nagbibigay ng klase ng tagapamagitan na humahawak sa lahat ng komunikasyon sa pagitan ng iba't ibang klase.

Pagpapatupad:

class Mediator {
    public static void sendMessage(User user, String msg){
        System.out.println(user.getName() + ": " + msg);
    }
}
class User {
    private String name;
    public User(String name){
        this.name  = name;
    }
    public String getName() {
        return name;
    }
    public void sendMessage(String msg){
        Mediator.sendMessage(this, msg);
    }
}

public class MediatorTest {//тест
    public static void main(String[] args) {
        User user1 = new User("user1");
        User user2 = new User("user2");
        user1.sendMessage("message1");
        user2.sendMessage("message2");
    }
}

Kadena ng Pananagutan

Paglalarawan :

Binibigyang-daan kang maiwasan ang mahigpit na pag-asa ng nagpadala ng kahilingan sa tatanggap nito, habang ang kahilingan ay maaaring iproseso ng ilang bagay.

Pagpapatupad:

interface Payment {
    void setNext(Payment payment);
    void pay();
}
class VisaPayment implements Payment {
    private Payment payment;
    public void setNext(Payment payment) {
        this.payment = payment;
    }
    public void pay() {
        System.out.println("Visa Payment");
    }
}
class PayPalPayment implements Payment {
    private Payment payment;
    public void setNext(Payment payment) {
        this.payment = payment;
    }
    public void pay() {
        System.out.println("PayPal Payment");
    }
}

public class ChainofResponsibilityTest {//тест
    public static void main(String[] args) {
        Payment visaPayment = new VisaPayment();
        Payment payPalPayment = new PayPalPayment();
        visaPayment.setNext(payPalPayment);
        visaPayment.pay();
    }
}

Tagamasid

Paglalarawan :

Nagbibigay-daan sa isang bagay na obserbahan ang mga pagkilos na nagaganap sa iba pang mga bagay.

Pagpapatupad:

import java.util.ArrayList;
import java.util.List;
interface Observer {
    void event(List<String> strings);
}
class University {
    private List<Observer> observers = new ArrayList<Observer>();
    private List<String> students = new ArrayList<String>();
    public void addStudent(String name) {
        students.add(name);
        notifyObservers();
    }
    public void removeStudent(String name) {
        students.remove(name);
        notifyObservers();
    }
    public void addObserver(Observer observer){
        observers.add(observer);
    }
    public void removeObserver(Observer observer) {
        observers.remove(observer);
    }
    public void notifyObservers(){
        for (Observer observer : observers) {
            observer.event(students);
        }
    }
}
class Director implements Observer {
    public void event(List<String> strings) {
        System.out.println("The list of students has changed: " + strings);
    }
}

public class ObserverTest {//тест
    public static void main(String[] args) {
        University university = new University();
        Director director = new Director();
        university.addStudent("Vaska");
        university.addObserver(director);
        university.addStudent("Anna");
        university.removeStudent("Vaska");
    }
}

Diskarte

Paglalarawan :

Tinutukoy ang isang bilang ng mga algorithm na nagpapahintulot sa pakikipag-ugnayan sa pagitan ng mga ito. Maaaring baguhin ang algorithm ng diskarte sa panahon ng pagpapatupad ng programa.

Pagpapatupad:

interface Strategy {
    void download(String file);
}
class DownloadWindownsStrategy implements Strategy {
    public void download(String file) {
        System.out.println("windows download: " + file);
    }
}
class DownloadLinuxStrategy implements Strategy {
    public void download(String file) {
        System.out.println("linux download: " + file);
    }
}
class Context {
    private Strategy strategy;
    public Context(Strategy strategy){
        this.strategy = strategy;
    }
    public void download(String file){
        strategy.download(file);
    }
}

public class StrategyTest {//тест
    public static void main(String[] args) {
        Context context = new Context(new DownloadWindownsStrategy());
        context.download("file.txt");
        context = new Context(new DownloadLinuxStrategy());
        context.download("file.txt");
    }
}

Utos

Paglalarawan :

Binibigyang-daan kang i-encapsulate ang iba't ibang mga operasyon sa magkakahiwalay na mga bagay.

Pagpapatupad:

interface Command {
    void execute();
}
class Car {
    public void startEngine() {
        System.out.println("запустить двигатель");
    }
    public void stopEngine() {
        System.out.println("остановить двигатель");
    }
}
class StartCar implements Command {
    Car car;
    public StartCar(Car car) {
        this.car = car;
    }
    public void execute() {
        car.startEngine();
    }
}
class StopCar implements Command {
    Car car;
    public StopCar(Car car) {
        this.car = car;
    }
    public void execute() {
        car.stopEngine();
    }
}
class CarInvoker {
    public Command command;
    public CarInvoker(Command command){
        this.command = command;
    }
    public void execute(){
        this.command.execute();
    }
}

public class CommandTest {//тест
    public static void main(String[] args) {
        Car car = new Car();
        StartCar startCar = new StartCar(car);
        StopCar stopCar = new StopCar(car);
        CarInvoker carInvoker = new CarInvoker(startCar);
        carInvoker.execute();
    }
}

Estado

Paglalarawan :

Nagbibigay-daan sa isang bagay na baguhin ang pag-uugali nito depende sa estado nito.

Pagpapatupad:

interface State {
    void doAction();
}
class StartPlay implements State {
    public void doAction() {
        System.out.println("start play");
    }
}
class StopPlay implements State {
    public void doAction() {
        System.out.println("stop play");
    }
}
class PlayContext implements State {
    private State state;
    public void setState(State state){
        this.state = state;
    }
    public void doAction() {
        this.state.doAction();
    }
}

public class StateTest {//тест
    public static void main(String[] args) {
        PlayContext playContext = new PlayContext();
        State startPlay = new StartPlay();
        State stopPlay = new StopPlay();
        playContext.setState(startPlay);
        playContext.doAction();
        playContext.setState(stopPlay);
        playContext.doAction();
    }
}

Bisita

Paglalarawan :

Ginagamit upang pasimplehin ang mga pagpapatakbo sa mga pagpapangkat ng mga kaugnay na bagay.

Pagpapatupad:

interface Visitor {
    void visit(SportCar sportCar);
    void visit(Engine engine);
    void visit(Whell whell);
}
interface Car {
    void accept(Visitor visitor);
}
class Engine implements Car {
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }
}
class Whell implements Car {
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }
}
class SportCar implements Car {
    Car[] cars;
    public SportCar(){
        cars = new Car[]{new Engine(), new Whell()};
    }
    public void accept(Visitor visitor) {
        for (int i = 0; i < cars.length; i++) {
            cars[i].accept(visitor);
        }
        visitor.visit(this);
    }
}
class CarVisitor implements Visitor {
    public void visit(SportCar computer) {
        print("car");
    }
    public void visit(Engine engine) {
        print("engine");
    }
    public void visit(Whell whell) {
        print("whell");
    }
    private void print(String string) {
        System.out.println(string);
    }
}

public class VisitorTest {//тест
    public static void main(String[] args) {
        Car computer = new SportCar();
        computer.accept(new CarVisitor());
    }
}

Interpreter

Paglalarawan :

Binibigyang-daan kang tumukoy ng isang simpleng grammar ng wika para sa isang domain ng problema.

Pagpapatupad:

interface Expression {
    String interpret(Context context);
}
class Context {
    public String getLowerCase(String s){
        return s.toLowerCase();
    }
    public String getUpperCase(String s){
        return s.toUpperCase();
    }
}
class LowerExpression implements Expression {
    private String s;
    public LoverExpression(String s) {
        this.s = s;
    }
    public String interpret(Context context) {
        return context.getLoverCase(s);
    }
}
class UpperExpression implements Expression {
    private String s;
    public UpperExpression(String s) {
        this.s = s;
    }
    public String interpret(Context context) {
        return context.getUpperCase(s);
    }
}

public class InterpreterTest {//тест
    public static void main(String[] args) {
        String str = "TesT";
        Context context = new Context();
        Expression loverExpression = new LoverExpression(str);
        str = loverExpression.interpret(context);
        System.out.println(str);
        Expression upperExpression = new UpperExpression(str);
        str = upperExpression.interpret(context);
        System.out.println(str);
    }
}

Tagapag-ulit

Paglalarawan :

Sunud-sunod na ina-access ang mga elemento ng isang object ng koleksyon nang hindi nalalaman ang pinagbabatayan nitong representasyon.

Pagpapatupad:

interface Iterator {
    boolean hasNext();
    Object next();
}
class Numbers {
    public int num[] = {1 , 2, 3};
    public Iterator getIterator() {
        return new NumbersIterator();
    }
    private class NumbersIterator implements Iterator {
        int ind;
        public boolean hasNext() {
            if(ind < num.length) return true;
            return false;
        }
        public Object next() {
            if(this.hasNext()) return num[ind++];
            return null;
        }
    }
}

public class IteratorTest {//тест
    public static void main(String[] args) {
        Numbers numbers = new Numbers();
        Iterator iterator = numbers.getIterator();
        while (iterator.hasNext()) {
            System.out.println(iterator.next());
        }
    }
}

Memento (Tagapangalaga)

Paglalarawan :

Binibigyang-daan kang i-save ang kasalukuyang estado ng bagay; ang estado na ito ay maaaring maibalik sa ibang pagkakataon. Hindi nakakasira ng encapsulation.

Pagpapatupad:

import java.util.ArrayList;
import java.util.List;
class Memento {
    private String name;
    private int age;
    public Memento(String name, int age){
        this.name = name;
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public int getAge() {
        return age;
    }
}
class User {
    private String name;
    private int age;
    public User(String name, int age) {
        this.name = name;
        this.age = age;
        System.out.println(String.format("create: name = %s, age = %s", name, age));
    }
    public Memento save(){
        System.out.println(String.format("save: name = %s, age = %s", name, age));
        return new Memento(name, age);
    }
    public void restore(Memento memento){
        name = memento.getName();
        age = memento.getAge();
        System.out.println(String.format("restore: name = %s, age = %s", name, age));
    }
}
class SaveUser {
    private List<Memento> list = new ArrayList<Memento>();
    public void add(Memento memento){
        list.

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