Add java design pattern code

design-patterns/java/adapter/AdapterDemo.java

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+public class AdapterDemo {
+    public static void main(String[] args) {
+        AudioPlayer audioPlayer = new AudioPlayer();
+
+        audioPlayer.play("mp3", "beyond_the_horizon.mp3");
+        audioPlayer.play("mp4", "alone.mp4");
+        audioPlayer.play("vlc", "far_far_away.vlc");
+        audioPlayer.play("avi", "mind_me.avi");
+    }
+}

design-patterns/java/adapter/AdvancedMediaPlayer.java

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+interface AdvancedMediaPlayer {
+    void playVlc(String fileName);
+    void playMp4(String fileName);
+}

design-patterns/java/adapter/AudioPlayer.java

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+class AudioPlayer implements MediaPlayer {
+    MediaAdapter mediaAdapter;
+
+    @Override
+    public void play(String audioType, String fileName) {
+        // inbuilt support to play mp3 music files
+        if (audioType.equalsIgnoreCase("mp3")) {
+            System.out.println("Playing mp3 file. Name: " + fileName);
+        }
+        // mediaAdapter is providing support to play other file formats
+        else if (audioType.equalsIgnoreCase("vlc") || audioType.equalsIgnoreCase("mp4")) {
+            mediaAdapter = new MediaAdapter(audioType);
+            mediaAdapter.play(audioType, fileName);
+        } else {
+            System.out.println("Invalid media. " + audioType + " format not supported");
+        }
+    }
+}

design-patterns/java/adapter/MediaAdapter.java

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+class MediaAdapter implements MediaPlayer {
+    AdvancedMediaPlayer advancedMusicPlayer;
+
+    public MediaAdapter(String audioType) {
+        if (audioType.equalsIgnoreCase("vlc")) {
+            advancedMusicPlayer = new VlcPlayer();
+        } else if (audioType.equalsIgnoreCase("mp4")) {
+            advancedMusicPlayer = new Mp4Player();
+        }
+    }
+
+    @Override
+    public void play(String audioType, String fileName) {
+        if (audioType.equalsIgnoreCase("vlc")) {
+            advancedMusicPlayer.playVlc(fileName);
+        } else if (audioType.equalsIgnoreCase("mp4")) {
+            advancedMusicPlayer.playMp4(fileName);
+        }
+    }
+}

design-patterns/java/adapter/MediaPlayer.java

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+interface MediaPlayer {
+    void play(String audioType, String fileName);
+}

design-patterns/java/adapter/Mp4Player.java

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+class Mp4Player implements AdvancedMediaPlayer {
+    @Override
+    public void playVlc(String fileName) {
+        // do nothing
+    }
+
+    @Override
+    public void playMp4(String fileName) {
+        System.out.println("Playing mp4 file. Name: " + fileName);
+    }
+}

design-patterns/java/adapter/VlcPlayer.java

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+class VlcPlayer implements AdvancedMediaPlayer {
+    @Override
+    public void playVlc(String fileName) {
+        System.out.println("Playing vlc file. Name: " + fileName);
+    }
+
+    @Override
+    public void playMp4(String fileName) {
+        // do nothing
+    }
+}

design-patterns/java/builder/BuilderDemo.java

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+public class BuilderDemo {
+    public static void main(String[] args) {
+        Waiter waiter = new Waiter();
+        PizzaBuilder hawaiianPizzaBuilder = new HawaiianPizzaBuilder();
+        PizzaBuilder spicyPizzaBuilder = new SpicyPizzaBuilder();
+
+        waiter.setPizzaBuilder(hawaiianPizzaBuilder);
+        waiter.constructPizza();
+        Pizza hawaiianPizza = waiter.getPizza();
+        System.out.println(hawaiianPizza);
+
+        waiter.setPizzaBuilder(spicyPizzaBuilder);
+        waiter.constructPizza();
+        Pizza spicyPizza = waiter.getPizza();
+        System.out.println(spicyPizza);
+    }
+}

design-patterns/java/builder/HawaiianPizzaBuilder.java

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+class HawaiianPizzaBuilder implements PizzaBuilder {
+    private Pizza pizza;
+
+    public HawaiianPizzaBuilder() { this.pizza = new Pizza(); }
+
+    public void buildDough()   { pizza.setDough("cross"); }
+    public void buildSauce()   { pizza.setSauce("mild"); }
+    public void buildTopping() { pizza.setTopping("ham and pineapple"); }
+    public Pizza getPizza()    { return this.pizza; }
+}

design-patterns/java/builder/Pizza.java

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+class Pizza {
+    private String dough = "";
+    private String sauce = "";
+    private String topping = "";
+
+    public void setDough(String dough)     { this.dough = dough; }
+    public void setSauce(String sauce)     { this.sauce = sauce; }
+    public void setTopping(String topping) { this.topping = topping; }
+
+    public String toString() {
+        return "Pizza with " + dough + " dough, " + sauce + " sauce, and " + topping + " topping.";
+    }
+}

design-patterns/java/builder/PizzaBuilder.java

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+interface PizzaBuilder {
+    void buildDough();
+    void buildSauce();
+    void buildTopping();
+    Pizza getPizza();
+}

design-patterns/java/builder/SpicyPizzaBuilder.java

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+class SpicyPizzaBuilder implements PizzaBuilder {
+    private Pizza pizza;
+
+    public SpicyPizzaBuilder() { this.pizza = new Pizza(); }
+
+    public void buildDough()   { pizza.setDough("pan baked"); }
+    public void buildSauce()   { pizza.setSauce("hot"); }
+    public void buildTopping() { pizza.setTopping("pepperoni and jalapeno"); }
+    public Pizza getPizza()    { return this.pizza; }
+}

design-patterns/java/builder/Waiter.java

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+class Waiter {
+    private PizzaBuilder pizzaBuilder;
+
+    public void setPizzaBuilder(PizzaBuilder pb) { pizzaBuilder = pb; }
+
+    public Pizza getPizza() { return pizzaBuilder.getPizza(); }
+
+    public void constructPizza() {
+        pizzaBuilder.buildDough();
+        pizzaBuilder.buildSauce();
+        pizzaBuilder.buildTopping();
+    }
+}

design-patterns/java/command/Command.java

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+interface Command {
+    void execute();
+    void undo();
+}

design-patterns/java/command/CommandPatternDemo.java

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+public class CommandPatternDemo {
+    public static void main(String[] args) {
+        // Set up the receiver
+        Light livingRoomLight = new Light("Living Room");
+        Light kitchenLight = new Light("Kitchen");
+
+        // Create concrete commands
+        Command livingRoomLightOn = new LightOnCommand(livingRoomLight);
+        Command livingRoomLightOff = new LightOffCommand(livingRoomLight);
+        Command kitchenLightOn = new LightOnCommand(kitchenLight);
+        Command kitchenLightOff = new LightOffCommand(kitchenLight);
+
+        // Set up the invoker
+        RemoteControl remote = new RemoteControl();
+
+        // Use the invoker to execute commands
+        remote.setCommand(livingRoomLightOn);
+        remote.pressButton();
+        remote.setCommand(kitchenLightOn);
+        remote.pressButton();
+        remote.setCommand(livingRoomLightOff);
+        remote.pressButton();
+        remote.setCommand(kitchenLightOff);
+        remote.pressButton();
+
+        // Demonstrate undo
+        System.out.println("\nDemonstrating undo:");
+        remote.setCommand(livingRoomLightOn);
+        remote.pressButton();
+        remote.pressUndoButton();
+
+        // Demonstrate RemoteControlWithUndo
+        System.out.println("\nDemonstrating RemoteControlWithUndo:");
+        RemoteControlWithUndo advancedRemote = new RemoteControlWithUndo();
+        advancedRemote.addCommand(livingRoomLightOn);
+        advancedRemote.addCommand(kitchenLightOn);
+        advancedRemote.executeCommands();
+        advancedRemote.undoLastCommand();
+        advancedRemote.undoLastCommand();
+    }
+}

design-patterns/java/command/Light.java

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+class Light {
+    private boolean isOn = false;
+    private String location;
+
+    public Light(String location) {
+        this.location = location;
+    }
+
+    public void turnOn() {
+        isOn = true;
+        System.out.println(location + " light is now ON");
+    }
+
+    public void turnOff() {
+        isOn = false;
+        System.out.println(location + " light is now OFF");
+    }
+}

design-patterns/java/command/LightOffCommand.java

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+class LightOffCommand implements Command {
+    private Light light;
+
+    public LightOffCommand(Light light) {
+        this.light = light;
+    }
+
+    public void execute() {
+        light.turnOff();
+    }
+
+    public void undo() {
+        light.turnOn();
+    }
+}

design-patterns/java/command/LightOnCommand.java

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+class LightOnCommand implements Command {
+    private Light light;
+
+    public LightOnCommand(Light light) {
+        this.light = light;
+    }
+
+    public void execute() {
+        light.turnOn();
+    }
+
+    public void undo() {
+        light.turnOff();
+    }
+}

design-patterns/java/command/RemoteControl.java

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+class RemoteControl {
+    private Command command;
+
+    public void setCommand(Command command) {
+        this.command = command;
+    }
+
+    public void pressButton() {
+        command.execute();
+    }
+
+    public void pressUndoButton() {
+        command.undo();
+    }
+}

design-patterns/java/command/RemoteControlWithUndo.java

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+class RemoteControlWithUndo {
+    private List<Command> commands = new ArrayList<>();
+    private List<Command> undoCommands = new ArrayList<>();
+
+    public void addCommand(Command command) {
+        commands.add(command);
+    }
+
+    public void executeCommands() {
+        for (Command command : commands) {
+            command.execute();
+            undoCommands.add(command);
+        }
+        commands.clear();
+    }
+
+    public void undoLastCommand() {
+        if (!undoCommands.isEmpty()) {
+            Command lastCommand = undoCommands.remove(undoCommands.size() - 1);
+            lastCommand.undo();
+        }
+    }
+}

design-patterns/java/composite/CompositeDemo.java

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+public class CompositeDemo {
+    public static void main(String[] args) {
+        Developer dev1 = new Developer("John Doe", 100000);
+        Developer dev2 = new Developer("Jane Smith", 120000);
+        Designer designer = new Designer("Mike Johnson", 90000);
+
+        Manager engManager = new Manager("Emily Brown", 200000);
+        engManager.addEmployee(dev1);
+        engManager.addEmployee(dev2);
+        engManager.addEmployee(designer);
+
+        Manager generalManager = new Manager("David Wilson", 300000);
+        generalManager.addEmployee(engManager);
+
+        System.out.println("Company Structure:");
+        generalManager.showDetails();
+
+        System.out.println("\nTotal Salary Budget: $" + generalManager.getSalary());
+    }
+}

design-patterns/java/composite/Designer.java

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+class Designer implements Employee {
+    private String name;
+    private double salary;
+
+    public Designer(String name, double salary) {
+        this.name = name;
+        this.salary = salary;
+    }
+
+    @Override
+    public void showDetails() {
+        System.out.println("Designer: " + name + ", Salary: $" + salary);
+    }
+
+    @Override
+    public double getSalary() {
+        return salary;
+    }
+}

design-patterns/java/composite/Developer.java

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+class Developer implements Employee {
+    private String name;
+    private double salary;
+
+    public Developer(String name, double salary) {
+        this.name = name;
+        this.salary = salary;
+    }
+
+    @Override
+    public void showDetails() {
+        System.out.println("Developer: " + name + ", Salary: $" + salary);
+    }
+
+    @Override
+    public double getSalary() {
+        return salary;
+    }
+}

design-patterns/java/composite/Employee.java

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+interface Employee {
+    void showDetails();
+    double getSalary();
+}