جاوا ۾ ڊيزائن جا نمونا [حصو 2]

سڀني کي سلام. منهنجي پوئين مضمون ۾ ، مون مختصر طور تي هر نموني بيان ڪيو. هن مقالي ۾، مان ڏيکارڻ جي ڪوشش ڪندس، تفصيل سان، نمونن کي ڪيئن استعمال ڪجي.

تخليقي

سنگلٽن

وضاحت: ھڪڙي ھڪڙي مثال تائين ھڪڙي طبقي جي ٺاھڻ کي محدود ڪري ٿو، ۽ ھڪڙي ھڪڙي مثال تائين رسائي فراهم ڪري ٿو. ڪلاس جو ٺاھيندڙ خانگي آھي. طريقو getInstance()ڪلاس جو صرف هڪ مثال ٺاهي ٿو. عمل درآمد:

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

ڪارخانو

وضاحت: استعمال ڪيو ويندو آھي جڏھن اسان وٽ ھڪڙو سپر ڪلاس آھي ڪيترن ئي ذيلي ڪلاسن سان ۽ اسان کي ان پٽ جي بنياد تي ھڪڙو ذيلي ڪلاس واپس ڪرڻ جي ضرورت آھي. طبقي کي خبر ناهي ته ان کي ڪهڙي قسم جو اعتراض پيدا ڪرڻ گهرجي. شيون ان پٽ جي بنياد تي ٺاهيا ويا آهن. عمل درآمد:

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("uses Windows");
    }
}
class linuxOS implements OS {
    public void getOS () {
        System.out.println("uses Linux");
    }
}
class macOS implements OS {
    public void getOS () {
        System.out.println("uses macOS");
    }
}

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

خلاصو ڪارخانو

وضاحت: توهان کي ممڪن فيڪٽريز جي خاندان مان هڪ مخصوص فيڪٽري لاڳو ڪرڻ جي اجازت ڏئي ٿي. لاڳاپيل شين جو هڪ خاندان ٺاهي ٿو. وسعت ڏيڻ آسان. عمل درآمد:

interface Lada {
    long getLadaPrice();
}
interface Ferrari {
    long getFerrariPrice();
}
interface Porshe {
    long getPorshePrice();
}
interface InteAbsFactory {
    Lada getLada();
    Ferrari getFerrari();
    Porshe getPorshe();
}
class UaLadaImpl implements Lada { // First
    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();
    }
} // First
class RuLadaImpl implements Lada { // Second
    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();
    }
} // Second

public class AbstractFactoryTest { // Test
    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());
    }
}

تعمير ڪندڙ

وضاحت: سادي شيون استعمال ڪندي پيچيده اعتراض ٺاهڻ لاء استعمال ڪيو ويو. اهو آهستي آهستي هڪ ننڍڙي، سادي شئي مان هڪ وڏي شئي ٺاهي ٿو. توهان کي آخري پيداوار جي اندروني نمائندگي کي تبديل ڪرڻ جي اجازت ڏئي ٿي. عمل درآمد:

class Car {
    public void buildBase() {
        print("Building the base");
    }
    public void buildWheels() {
        print("Installing wheels");
    }
    public void buildEngine(Engine engine) {
        print("Installing engine: " + engine.getEngineType());
    }
    private void print(String msg){
        System.out.println(msg);
    }
}
interface Engine {
    String getEngineType();
}
class EngineOne implements Engine {
    public String getEngineType() {
        return "First engine";
    }
}
class EngineTwo implements Engine {
    public String getEngineType() {
        return "Second engine";
    }
}
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 EngineOne();
        car.buildEngine(engine);
        return car;
    }
}
class TwoBuilderImpl extends Builder {
    public TwoBuilderImpl(){
        car = new Car();
    }
    public Car buildCar() {
        car.buildBase();
        car.buildWheels();
        Engine engine = new EngineOne();
        car.buildEngine(engine);
        car.buildWheels();
        engine = new EngineTwo();
        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 { // Test
    public static void main(String[] args) {
        Build build = new Build(1);
        build.buildCar();
    }
}

پروٽوٽائپ

وضاحت: ڪارڪردگي کي بهتر بنائڻ ۾ مدد ڪري ٿي جڏهن نقلي شيون ٺاهيندي؛ هڪ نئين شئي ٺاهڻ جي بدران اهو هڪ موجوده اعتراض جو هڪ کلون ٺاهي ۽ واپس ڪري ٿو. موجوده شئي کي ڪلون ڪري ٿو. عمل درآمد:

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

ساخت وارو

اڊاپٽر

وضاحت: اسان اڊاپٽر نموني استعمال ڪري سگھون ٿا ٻن غير مطابقت واري انٽرفيس کي گڏ ڪرڻ لاءِ. اهو ٻن غير مطابقت رکندڙ شين جي وچ ۾ ڪنورٽر طور ڪم ڪري ٿو. عمل درآمد:

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

جامع

وضاحت: ھڪڙي طبقي کي استعمال ڪندي ڪيترن ئي شين کي ھڪڙي وڻ جي جوڙجڪ ۾ گروپ ڪريو. توهان کي هڪ واحد اعتراض ذريعي ڪيترن ئي طبقن سان ڪم ڪرڻ جي اجازت ڏئي ٿي. عمل درآمد:

import java.util.ArrayList;
import java.util.List;
interface Car {
    void draw(String color);
}
class SportsCar implements Car {
    public void draw(String color) {
        System.out.println("SportsCar 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 { // Test
    public static void main(String[] args) {
        Car sportsCar = new SportsCar();
        Car unknownCar = new UnknownCar();
        Drawing drawing = new Drawing();
        drawing.add(sportsCar);
        drawing.add(unknownCar);
        drawing.draw("green");
        drawing.clear();
        drawing.add(sportsCar);
        drawing.add(unknownCar);
        drawing.draw("white");
    }
}

پراڪسي

وضاحت: شين جي نمائندگي ڪري ٿو جيڪي ٻين شين کي ڪنٽرول ڪري سگھن ٿيون انهن جي طريقن جي ڪالن کي مداخلت ڪندي. توھان ڪري سگھوٿا اصل اعتراض جي طريقي واري ڪال کي. عمل درآمد:

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("Loading " + file);
    }
    public void display() {
        System.out.println("Displaying " + 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 { // Test
    public static void main(String[] args) {
        Image image = new ProxyImage("test.jpg");
        image.display();
        image.display();
    }
}

فلائي ويٽ

وضاحت: شين کي ٻيهر استعمال ڪرڻ بدران هڪجهڙائي واري شين جو وڏو تعداد ٺاهڻ. ياداشت بچائيندو آهي. عمل درآمد:

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 { // Test
    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();
        }
    }
}

منهن

وضاحت: لڪايو ڪلاسن جو هڪ پيچيده نظام سڀني ڪالن کي هڪ اعتراض ۾ شامل ڪندي. ڪيترن ئي پيچيده شين جي ميٿڊ ڪالز کي ھڪڙي اعتراض ۾ رکي ٿو. عمل درآمد:

interface Car {
    void start();
    void stop();
}
class Key implements Car {
    public void start() {
        System.out.println("Insert keys");
    }
    public void stop() {
        System.out.println("Remove keys");
    }
}
class Engine implements Car {
    public void start() {
        System.out.println("Start engine");
    }
    public void stop() {
        System.out.println ("Stop engine");
    }
}
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 { // Test
    public static void main(String[] args) {
        Facade facade = new Facade();
        facade.startCar();
        System.out.println();
        facade.stoptCar();
    }
}

پل

وضاحت: تجريد کان عمل کي الڳ ڪري ٿو، اهو ممڪن بڻائي ٿو ته هر هڪ ٻئي کان آزاديء سان تبديل ڪرڻ. مخصوص طبقن کي انٽرفيس کي لاڳو ڪندڙ طبقن کان آزاد بڻائي ٿو. عمل درآمد:

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

سينگار ڪندڙ

وضاحت: موجوده شئي ۾ نئين ڪارڪردگي شامل ڪري ٿو بغير ان جي جوڙجڪ ۾. عمل درآمد:

interface Car {
    void draw();
}
class SportsCar implements Car {
    public void draw() {
        System.out.println("SportsCar");
    }
}
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 { // Test
    public static void main(String[] args) {
        Car sportsCar = new SportsCar();
        Car blueUnknownCar = new BlueCarDecorator(new UnknownCar());
        sportsCar.draw();
        System.out.println();
        blueUnknownCar.draw();
    }
}

رويي وارو

ٽيمپليٽ جو طريقو

وضاحت: توهان کي هڪ بنيادي الورورٿم جي وضاحت ڪرڻ جي اجازت ڏئي ٿي ۽ اولاد کي اجازت ڏئي ٿي ته ان جي مجموعي جوڙجڪ کي تبديل ڪرڻ کان سواءِ الگورٿم جي ڪجهه مرحلن کي اوور رائڊ ڪري. عمل درآمد:

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

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

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

ثالث

وضاحت: هڪ وچولي ڪلاس مهيا ڪري ٿو جيڪو مختلف طبقن جي وچ ۾ سڀني رابطي کي سنڀاليندو آهي. عمل درآمد:

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

ذميواري جو سلسلو

وضاحت: اهو ممڪن بڻائي ٿو ته درخواست جي موڪليندڙ ۽ وصول ڪندڙ جي وچ ۾ سخت انحصار کان بچڻ؛ ان کان علاوه، درخواست تي عمل ڪري سگھجي ٿو ڪيترن ئي شين طرفان. عمل درآمد:

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

مبصر

وضاحت: ھڪڙي اعتراض کي ڏسڻ جي اجازت ڏئي ٿي ته ٻين شين ۾ ڇا ٿئي. عمل درآمد:

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

حڪمت عملي

وضاحت: الگورتھم جو ھڪڙو سيٽ بيان ڪري ٿو ۽ انھن کي رابطي جي اجازت ڏئي ٿو. حڪمت عملين لاءِ اجازت ڏئي ٿو (الگورٿمز) کي هلائڻ وقت تبديل ڪيو وڃي. عمل درآمد:

interface Strategy {
    void download(String file);
}
class WindowsDownloadStrategy implements Strategy {
    public void download(String file) {
        System.out.println("windows download: " + file);
    }
}
class LinuxDownloadStrategy 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 { // Test
    public static void main(String[] args) {
        Context context = new Context(new WindowsDownloadStrategy());
        context.download("file.txt");
        context = new Context(new LinuxDownloadStrategy());
        context.download("file.txt");
    }
}

حڪم

وضاحت: توهان کي اجازت ڏئي ٿي ته مختلف عملن کي انفرادي شين ۾ شامل ڪري. عمل درآمد:

interface Command {
    void execute();
}
class Car {
    public void startEngine() {
        System.out.println("Start engine");
    }
    public void stopEngine() {
        System.out.println ("Stop engine");
    }
}
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 { // Test
    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();
    }
}

رياست

وضاحت: هڪ اعتراض کي اجازت ڏئي ٿو ته ان جي رويي کي تبديل ڪري ان جي حالت تي منحصر آهي. عمل درآمد:

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 { // Test
    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();
    }
}

گهمڻ وارو

وضاحت: لاڳاپيل شين جي گروپن تي عمل کي آسان ڪرڻ لاء استعمال ڪيو ويو. عمل درآمد:

interface Visitor {
    void visit(SportsCar sportsCar);
    void visit(Engine engine);
    void visit(Wheel wheel);
}
interface Car {
    void accept(Visitor visitor);
}
class Engine implements Car {
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }
}
class Wheel implements Car {
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }
}
class SportsCar implements Car {
    Car[] cars;
    public SportsCar(){
        cars = new Car[]{new Engine(), new Wheel()};
    }
    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(SportsCar computer) {
        print("car");
    }
    public void visit(Engine engine) {
        print("engine");
    }
    public void visit(Wheel wheel) {
        print("wheel");
    }
    private void print(String string) {
        System.out.println(string);
    }
}

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

مترجم

وضاحت: توهان کي اجازت ڏئي ٿي ته مسئلي جي ڊومين ۾ هڪ سادي ٻولي جي گرامر کي بيان ڪريو. عمل درآمد:

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 LowerExpression(String s) {
        this.s = s;
    }
    public String interpret(Context context) {
        return context.getLowerCase(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 { // Test
    public static void main(String[] args) {
        String str = "TesT";
        Context context = new Context();
         Expression lowerExpression = new LowerExpression(str);
         str = lowerExpression.interpret(context);
        System.out.println(str);
        Expression upperExpression = new UpperExpression(str);
        str = upperExpression.interpret(context);
        System.out.println(str);
    }
}

ورجائيندڙ

وضاحت: هڪ آئٽرٽر ترتيب سان ان جي بنيادي شڪل کي ڄاڻڻ کان سواء هڪ مجموعي جي عناصر تائين رسائي ڪري ٿو. عمل درآمد:

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

يادگار

وضاحت: توهان کي ڪنهن شئي جي موجوده حالت کي بچائڻ جي اجازت ڏئي ٿي؛ هن رياست کي بعد ۾ بحال ڪري سگهجي ٿو. encapsulation جي ڀڃڪڙي نه ڪندو آھي. عمل درآمد:

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.add(memento);
    }
    public Memento get(int ind){
        return list.get(ind);
    }
}

public class MementoTest { // Test
    public static void main(String[] args) {
        SaveUser saveUser = new SaveUser();
        User user1 = new User("Peter", 17);
        User user2 = new User("Ian", 19);
        saveUser.add(user1.save());
        user1.restore(saveUser.get(0));
    }
}

سٺي قسمت پروگرامنگ!