added builder example

src/lab5_adapter/ex1/Engineer.java

@@ -0,0 +1,13 @@
+package lab5_adapter.ex1;
+
+public class Engineer {
+    private String name;
+    public Engineer(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public String toString() {
+        return "Engineer " + name;
+    }
+}

src/lab5_adapter/ex1/Machine.java

@@ -0,0 +1,10 @@
+package lab5_adapter.ex1;
+
+public interface Machine {
+    int getNumberOfCapsules();
+    boolean isCompletelyUp();
+    void stop();
+
+    void setNumberOfCapsules(int capsules);
+    void setCompletelyUp(boolean completelyUp);
+}

src/lab5_adapter/ex1/MachineAdapter.java

@@ -0,0 +1,44 @@
+package lab5_adapter.ex1;
+
+public class MachineAdapter implements NewMachineInterface {
+    private OldMachine machine;
+
+    public MachineAdapter(OldMachine machine) {
+        this.machine = machine;
+    }
+
+    @Override
+    public int getNumberOfCapsules() {
+        return machine.getNumberOfCapsules();
+    }
+
+    @Override
+    public boolean isCompletelyUp() {
+        return machine.isCompletelyUp();
+    }
+
+    @Override
+    public void stop() {
+        machine.stop();
+    }
+
+    @Override
+    public void setNumberOfCapsules(int capsules) {
+        machine.setNumberOfCapsules(capsules);
+    }
+
+    @Override
+    public void setCompletelyUp(boolean completelyUp) {
+        machine.setCompletelyUp(completelyUp);
+    }
+
+    @Override
+    public Engineer getEngineer() {
+        return null;
+    }
+
+    @Override
+    public String toString() {
+        return machine.toString() + ", supervised by engineer " + getEngineer();
+    }
+}

src/lab5_adapter/ex1/Main.java

@@ -0,0 +1,27 @@
+package lab5_adapter.ex1;
+
+public class Main {
+    public static void main(String[] args) {
+        Engineer engineer1 = new Engineer("Jean");
+        Engineer engineer2 = new Engineer("Maria");
+        Machine machine1 = new NewMachine("1159190947", engineer1);
+        Machine machine2 = new NewMachine("1247233941", engineer1);
+        Machine machine3 = new NewMachine("258952499", engineer2);
+        OldMachine oldMachine = new OldMachine("603742814");
+        Machine machine4 = new MachineAdapter(oldMachine);
+
+        machine1.setNumberOfCapsules(30);
+        machine2.setNumberOfCapsules(20);
+        machine3.setNumberOfCapsules(40);
+        oldMachine.setNumberOfCapsules(80);
+        //Machine 1159190947 is currently processing 30 capsules, supervised by engineer Engineer Jean
+        //Machine 1247233941 is currently processing 20 capsules, supervised by engineer Engineer Jean
+        //Machine 258952499 is currently processing 40 capsules, supervised by engineer Engineer Maria
+        //Machine 603742814 is currently processing 80 capsules, supervised by engineer null
+
+        System.out.println(machine1);
+        System.out.println(machine2);
+        System.out.println(machine3);
+        System.out.println(machine4);
+    }
+}

src/lab5_adapter/ex1/NewMachine.java

@@ -0,0 +1,19 @@
+package lab5_adapter.ex1;
+
+public class NewMachine extends OldMachine implements NewMachineInterface {
+    private Engineer engineer;
+
+    public NewMachine(String name, Engineer engineer) {
+        super(name);
+        this.engineer = engineer;
+    }
+
+    public Engineer getEngineer() {
+        return engineer;
+    }
+
+    @Override
+    public String toString() {
+        return super.toString() + ", supervised by engineer " + getEngineer();
+    }
+}

src/lab5_adapter/ex1/NewMachineInterface.java

@@ -0,0 +1,5 @@
+package lab5_adapter.ex1;
+
+public interface NewMachineInterface extends Machine {
+    Engineer getEngineer();
+}

src/lab5_adapter/ex1/OldMachine.java

@@ -0,0 +1,39 @@
+package lab5_adapter.ex1;
+
+public class OldMachine implements Machine {
+    private String name;
+    private int capsules = 0;
+    private boolean completelyUp = false;
+
+    public OldMachine(String name) {
+        this.name = name;
+    }
+
+    public void setNumberOfCapsules(int capsules) {
+        this.capsules = capsules;
+    }
+
+    public void setCompletelyUp(boolean completelyUp) {
+        this.completelyUp = completelyUp;
+    }
+
+    @Override
+    public int getNumberOfCapsules() {
+        return capsules;
+    }
+
+    @Override
+    public boolean isCompletelyUp() {
+        return completelyUp;
+    }
+
+    @Override
+    public void stop() {
+        System.out.println("Stopping machine " + name);
+    }
+
+    @Override
+    public String toString() {
+        return "Machine " + name + " is currently processing " + getNumberOfCapsules() + " capsules";
+    }
+}

src/lab6_template_method/ex1/HellsKitchen.java

@@ -0,0 +1,32 @@
+package lab6_template_method.ex1;
+
+public class HellsKitchen extends Restaurant {
+    public HellsKitchen(String name) {
+        super("HK " + name);
+    }
+
+    @Override
+    public void prepareVegetables() {
+        log("Preparing nice salad");
+    }
+
+    @Override
+    public void prepareMainMenu() {
+        log("Creating flavorful dish");
+    }
+
+    @Override
+    public void prepareCheese() {
+        log("Preparing finest cheese");
+    }
+
+    @Override
+    public void prepareDessert() {
+        log("Giving birth to awesome dessert");
+    }
+
+    @Override
+    public void prepareCoffee() {
+        log("Brewing the best coffee");
+    }
+}

src/lab6_template_method/ex1/MacDonalds.java

@@ -0,0 +1,32 @@
+package lab6_template_method.ex1;
+
+public class MacDonalds extends Restaurant {
+    public MacDonalds(String name) {
+        super("McDonalds " + name);
+    }
+
+    @Override
+    public void prepareVegetables() {
+        log("Vegetables ? What's that ?");
+    }
+
+    @Override
+    public void prepareMainMenu() {
+        log("McChicken incoming");
+    }
+
+    @Override
+    public void prepareCheese() {
+        log("Hmmm, creamy cheese");
+    }
+
+    @Override
+    public void prepareDessert() {
+        log("Preparing McFlurry");
+    }
+
+    @Override
+    public void prepareCoffee() {
+        log("Preparing short and hot coffee");
+    }
+}

src/lab6_template_method/ex1/Main.java

@@ -0,0 +1,11 @@
+package lab6_template_method.ex1;
+
+public class Main {
+    public static void main(String[] args) {
+        Restaurant r1 = new MacDonalds("Sion");
+        Restaurant r2 = new HellsKitchen("London");
+
+        r1.prepareDinner();
+        r2.prepareDinner();
+    }
+}

src/lab6_template_method/ex1/Restaurant.java

@@ -0,0 +1,36 @@
+package lab6_template_method.ex1;
+
+public abstract class Restaurant {
+    private String name;
+    public Restaurant(String name) {
+        this.name = name;
+    }
+
+    public final void prepareDinner() {
+        serveWater();
+        prepareVegetables();
+        prepareMainMenu();
+        prepareCheese();
+        prepareDessert();
+        prepareCoffee();
+        cleanTable();
+    }
+
+    protected void log(String msg) {
+        System.out.println("[" + name + "] " + msg);
+    }
+
+    protected final void serveWater() {
+        log("Serving water");
+    }
+
+    protected final void cleanTable() {
+        log("Cleaning table");
+    }
+
+    protected abstract void prepareVegetables();
+    protected abstract void prepareMainMenu();
+    protected abstract void prepareCheese();
+    protected abstract void prepareDessert();
+    protected abstract void prepareCoffee();
+}

src/lab7_state/ex1/Machine.java

@@ -0,0 +1,101 @@
+package lab7_state.ex1;
+
+import lab7_state.ex1.states.*;
+
+public class Machine {
+    private MachineState currentState;
+    private final MachineState offState;
+    private final MachineState idleState;
+    private final MachineState choiceState;
+    private final MachineState serviceNeededState;
+    private final MachineState coffeeReadyState;
+
+    private int cups;
+    private boolean jammed = false;
+
+    public Machine() {
+        offState = new OffState(this);
+        idleState = new IdleState(this);
+        choiceState = new ChoiceState(this);
+        serviceNeededState = new ServiceNeededState(this);
+        coffeeReadyState = new CoffeeReadyState(this);
+        currentState = offState;
+        this.setCups(3);
+    }
+
+    public MachineState getOffState() {
+        return offState;
+    }
+
+    public MachineState getIdleState() {
+        return idleState;
+    }
+
+    public MachineState getChoiceState() {
+        return choiceState;
+    }
+
+    public MachineState getServiceNeededState() {
+        return serviceNeededState;
+    }
+
+    public MachineState getCoffeeReadyState() {
+        return coffeeReadyState;
+    }
+
+    public void returnMoney(double value) {
+        System.out.println("Returning CHF " + value);
+    }
+
+    public void setCurrentState(MachineState currentState) {
+        System.out.println(this.currentState.toString() + " -> " + currentState);
+        this.currentState = currentState;
+    }
+
+    public void powerUp() {
+        currentState.powerUp();
+    }
+
+    public void insertCoin(double value) {
+        currentState.insertCoin(value);
+    }
+
+    public void returnCoin() {
+        currentState.returnCoin();
+    }
+
+    public void pushButton() {
+        currentState.pushButton();
+    }
+
+    public void resetButton() {
+        currentState.reset();
+    }
+
+    public void removeCup() {
+        currentState.removeCup();
+    }
+
+    public void setCups(int cups) {
+        this.cups = cups;
+    }
+
+    public boolean hasCups() {
+        return cups != 0;
+    }
+
+    public boolean hasCoffee() {
+        return true;
+    }
+
+    public boolean isJammed() {
+        return jammed;
+    }
+
+    public void makeCoffee() {
+        cups--;
+        if (Math.random() < 0.2) {
+            jammed = true;
+        }
+    }
+}

src/lab7_state/ex1/MachineState.java

@@ -0,0 +1,21 @@
+package lab7_state.ex1;
+
+public abstract class MachineState {
+    protected Machine machine;
+
+    public MachineState(Machine machine) {
+        this.machine = machine;
+    }
+
+    protected void powerUp() {}
+    protected void insertCoin(double value) {}
+    protected void returnCoin() {}
+    protected void reset() {}
+    protected void pushButton() {}
+    protected void removeCup() {}
+
+    @Override
+    public String toString() {
+        return getClass().getSimpleName();
+    }
+}

src/lab7_state/ex1/Main.java

@@ -0,0 +1,29 @@
+package lab7_state.ex1;
+
+public class Main {
+    public static void main(String[] args) {
+        Machine machine = new Machine();
+        System.out.println("A");
+        machine.powerUp();
+        machine.insertCoin(1);
+
+        System.out.println("B");
+        machine.insertCoin(0.25);
+        machine.returnCoin();
+
+        System.out.println("C");
+        machine.insertCoin(0.25);
+        machine.pushButton();
+        machine.removeCup();
+
+        for (int i = 0; i < 4; i++) {
+            System.out.println("D" + i);
+            machine.insertCoin(0.25);
+            machine.pushButton();
+            machine.removeCup();
+        }
+
+        System.out.println("E");
+        machine.resetButton();
+    }
+}

src/lab7_state/ex1/states/ChoiceState.java

@@ -0,0 +1,32 @@
+package lab7_state.ex1.states;
+
+import lab7_state.ex1.Machine;
+import lab7_state.ex1.MachineState;
+
+public class ChoiceState extends MachineState {
+    public ChoiceState(Machine machine) {
+        super(machine);
+    }
+
+    @Override
+    protected void returnCoin() {
+        machine.returnMoney(0.25);
+        machine.setCurrentState(machine.getIdleState());
+    }
+
+    @Override
+    protected void pushButton() {
+        if (!machine.hasCups()) {
+            System.out.println("The machine is out of cups");
+        } else if (!machine.hasCoffee()) {
+            System.out.println("The machine is out of coffee beans");
+        } else if (machine.isJammed()) {
+            System.out.println("The machine is jammed");
+        } else {
+            machine.makeCoffee();
+            machine.setCurrentState(machine.getCoffeeReadyState());
+            return;
+        }
+        machine.setCurrentState(machine.getServiceNeededState());
+    }
+}

src/lab7_state/ex1/states/CoffeeReadyState.java

@@ -0,0 +1,15 @@
+package lab7_state.ex1.states;
+
+import lab7_state.ex1.Machine;
+import lab7_state.ex1.MachineState;
+
+public class CoffeeReadyState extends MachineState {
+    public CoffeeReadyState(Machine machine) {
+        super(machine);
+    }
+
+    @Override
+    protected void removeCup() {
+        machine.setCurrentState(machine.getIdleState());
+    }
+}

src/lab7_state/ex1/states/IdleState.java

@@ -0,0 +1,20 @@
+package lab7_state.ex1.states;
+
+import lab7_state.ex1.Machine;
+import lab7_state.ex1.MachineState;
+
+public class IdleState extends MachineState {
+    public IdleState(Machine machine) {
+        super(machine);
+    }
+
+    @Override
+    protected void insertCoin(double value) {
+        if (value != 0.25) {
+            machine.returnMoney(value);
+        } else {
+            System.out.println("Please choose your coffee");
+            machine.setCurrentState(machine.getChoiceState());
+        }
+    }
+}

src/lab7_state/ex1/states/OffState.java

@@ -0,0 +1,15 @@
+package lab7_state.ex1.states;
+
+import lab7_state.ex1.Machine;
+import lab7_state.ex1.MachineState;
+
+public class OffState extends MachineState {
+    public OffState(Machine machine) {
+        super(machine);
+    }
+
+    @Override
+    protected void powerUp() {
+        machine.setCurrentState(machine.getIdleState());
+    }
+}

src/lab7_state/ex1/states/ServiceNeededState.java

@@ -0,0 +1,15 @@
+package lab7_state.ex1.states;
+
+import lab7_state.ex1.Machine;
+import lab7_state.ex1.MachineState;
+
+public class ServiceNeededState extends MachineState {
+    public ServiceNeededState(Machine machine) {
+        super(machine);
+    }
+
+    @Override
+    protected void reset() {
+        machine.setCurrentState(machine.getIdleState());
+    }
+}

src/lab7_state/ex2/Main.java

@@ -0,0 +1,25 @@
+package lab7_state.ex2;
+
+public class Main {
+    public static void main(String[] args) {
+        User user = new User("Baryhobal");
+        user.connect();
+        user.enter();
+        user.leave();
+
+        user.enter();
+        user.ask();
+        user.leave();
+
+        user.enter();
+        user.ask();
+        user.handOver();
+        user.leave();
+
+        user.enter();
+        user.ask();
+        user.handOver();
+        user.over();
+        user.leave();
+    }
+}

src/lab7_state/ex2/User.java

@@ -0,0 +1,71 @@
+package lab7_state.ex2;
+
+import lab7_state.ex2.states.*;
+
+public class User {
+    private String name;
+    private UserState currentState;
+    private UserState unregisteredState;
+    private UserState registeredState;
+    private UserState inMeetingState;
+    private UserState waitingToSpeakState;
+    private UserState speakingState;
+
+    public User(String name) {
+        this.name = name;
+        unregisteredState = new UnregisteredState(this);
+        registeredState = new RegisteredState(this);
+        inMeetingState = new InMeetingState(this);
+        waitingToSpeakState = new WaitingToSpeakState(this);
+        speakingState = new SpeakingState(this);
+        currentState = unregisteredState;
+    }
+
+    public void setCurrentState(UserState currentState) {
+        this.currentState = currentState;
+    }
+
+    public UserState getUnregisteredState() {
+        return unregisteredState;
+    }
+
+    public UserState getRegisteredState() {
+        return registeredState;
+    }
+
+    public UserState getInMeetingState() {
+        return inMeetingState;
+    }
+
+    public UserState getWaitingToSpeakState() {
+        return waitingToSpeakState;
+    }
+
+    public UserState getSpeakingState() {
+        return speakingState;
+    }
+
+    public void connect() {
+        currentState.connect();
+    }
+    public void enter() {
+        currentState.enter();
+    }
+    public void leave() {
+        currentState.leave();
+    }
+    public void ask() {
+        currentState.ask();
+    }
+    public void handOver() {
+        currentState.handOver();
+    }
+    public void over() {
+        currentState.over();
+    }
+
+    @Override
+    public String toString() {
+        return "User " + name;
+    }
+}

src/lab7_state/ex2/UserState.java

@@ -0,0 +1,18 @@
+package lab7_state.ex2;
+
+public abstract class UserState {
+    protected User user;
+    public UserState(User user) {
+        this.user = user;
+    }
+    protected void log(String msg) {
+        System.out.println("[" + user + "] " + msg);
+    }
+
+    public void connect() {};
+    public void enter() {};
+    public void leave() {};
+    public void ask() {};
+    public void handOver() {};
+    public void over() {};
+}

src/lab7_state/ex2/states/InMeetingState.java

@@ -0,0 +1,22 @@
+package lab7_state.ex2.states;
+
+import lab7_state.ex2.User;
+import lab7_state.ex2.UserState;
+
+public class InMeetingState extends UserState {
+    public InMeetingState(User user) {
+        super(user);
+    }
+
+    @Override
+    public void leave() {
+        user.setCurrentState(user.getRegisteredState());
+        log("Left meeting");
+    }
+
+    @Override
+    public void ask() {
+        user.setCurrentState(user.getWaitingToSpeakState());
+        log("Asking to speak");
+    }
+}

src/lab7_state/ex2/states/RegisteredState.java

@@ -0,0 +1,16 @@
+package lab7_state.ex2.states;
+
+import lab7_state.ex2.User;
+import lab7_state.ex2.UserState;
+
+public class RegisteredState extends UserState {
+    public RegisteredState(User user) {
+        super(user);
+    }
+
+    @Override
+    public void enter() {
+        user.setCurrentState(user.getInMeetingState());
+        log("Entered meeting");
+    }
+}

src/lab7_state/ex2/states/SpeakingState.java

@@ -0,0 +1,22 @@
+package lab7_state.ex2.states;
+
+import lab7_state.ex2.User;
+import lab7_state.ex2.UserState;
+
+public class SpeakingState extends UserState {
+    public SpeakingState(User user) {
+        super(user);
+    }
+
+    @Override
+    public void over() {
+        user.setCurrentState(user.getInMeetingState());
+        log("Finished speaking");
+    }
+
+    @Override
+    public void leave() {
+        user.setCurrentState(user.getRegisteredState());
+        log("Finished speaking, left meeting");
+    }
+}

src/lab7_state/ex2/states/UnregisteredState.java

@@ -0,0 +1,16 @@
+package lab7_state.ex2.states;
+
+import lab7_state.ex2.User;
+import lab7_state.ex2.UserState;
+
+public class UnregisteredState extends UserState {
+    public UnregisteredState(User user) {
+        super(user);
+    }
+
+    @Override
+    public void connect() {
+        user.setCurrentState(user.getRegisteredState());
+        log("Registered");
+    }
+}

src/lab7_state/ex2/states/WaitingToSpeakState.java

@@ -0,0 +1,22 @@
+package lab7_state.ex2.states;
+
+import lab7_state.ex2.User;
+import lab7_state.ex2.UserState;
+
+public class WaitingToSpeakState extends UserState {
+    public WaitingToSpeakState(User user) {
+        super(user);
+    }
+
+    @Override
+    public void leave() {
+        user.setCurrentState(user.getRegisteredState());
+        log("Lost patience, left meeting");
+    }
+
+    @Override
+    public void handOver() {
+        user.setCurrentState(user.getSpeakingState());
+        log("Starts speaking");
+    }
+}

src/learn/simple_adapter/Adaptee.java

@@ -0,0 +1,7 @@
+package learn.simple_adapter;
+
+public class Adaptee {
+    public void specificRequest() {
+        System.out.println("Specific Request");
+    }
+}

src/learn/simple_adapter/Adapter.java

@@ -0,0 +1,14 @@
+package learn.simple_adapter;
+
+public class Adapter implements Target {
+    private Adaptee adaptee;
+
+    public Adapter(Adaptee adaptee) {
+        this.adaptee = adaptee;
+    }
+
+    @Override
+    public void request() {
+        adaptee.specificRequest();
+    }
+}

src/learn/simple_adapter/Main.java

@@ -0,0 +1,9 @@
+package learn.simple_adapter;
+
+public class Main {
+    public static void main(String[] args) {
+        Adaptee adaptee = new Adaptee();
+        Target adapter = new Adapter(adaptee);
+        adapter.request();
+    }
+}

src/learn/simple_adapter/Target.java

@@ -0,0 +1,5 @@
+package learn.simple_adapter;
+
+public interface Target {
+    void request();
+}

src/learn/simple_builder/Builder.java

@@ -0,0 +1,16 @@
+package learn.simple_builder;
+
+public abstract class Builder {
+    protected Product product;
+
+    public void setProduct(Product product) {
+        this.product = product;
+    }
+    public Product getProduct() {
+        return product;
+    }
+
+    public abstract void buildPartA();
+    public abstract void buildPartB();
+    public abstract void buildPartC();
+}

src/learn/simple_builder/ConcreteBuilder.java

@@ -0,0 +1,18 @@
+package learn.simple_builder;
+
+public class ConcreteBuilder extends Builder {
+    @Override
+    public void buildPartA() {
+        product.setPartA("material 1");
+    }
+
+    @Override
+    public void buildPartB() {
+        product.setPartB("material 2");
+    }
+
+    @Override
+    public void buildPartC() {
+        product.setPartC("material 3");
+    }
+}

src/learn/simple_builder/Director.java

@@ -0,0 +1,18 @@
+package learn.simple_builder;
+
+public class Director {
+    private Builder builder;
+    private Product product;
+
+    public void setBuilder(Builder builder) {
+        this.builder = builder;
+        product = new Product();
+        this.builder.setProduct(product);
+    }
+
+    public void construct() {
+        builder.buildPartA();
+        builder.buildPartB();
+        builder.buildPartC();
+    }
+}

src/learn/simple_builder/Main.java

@@ -0,0 +1,12 @@
+package learn.simple_builder;
+
+public class Main {
+    public static void main(String[] args) {
+        Builder builder = new ConcreteBuilder();
+        Director director = new Director();
+        director.setBuilder(builder);
+        director.construct();
+        Product finalProduct = builder.getProduct();
+        System.out.println(finalProduct);
+    }
+}

src/learn/simple_builder/Product.java

@@ -0,0 +1,28 @@
+package learn.simple_builder;
+
+public class Product {
+    private String partA;
+    private String partB;
+    private String partC;
+
+    @Override
+    public String toString() {
+        return "Product{" +
+                "partA='" + partA + '\'' +
+                ", partB='" + partB + '\'' +
+                ", partC='" + partC + '\'' +
+                '}';
+    }
+
+    public void setPartA(String partA) {
+        this.partA = partA;
+    }
+
+    public void setPartB(String partB) {
+        this.partB = partB;
+    }
+
+    public void setPartC(String partC) {
+        this.partC = partC;
+    }
+}

src/learn/simple_state/Context.java

@@ -0,0 +1,34 @@
+package learn.simple_state;
+
+public class Context {
+    private State onState;
+    private State offState;
+
+    private State currentState;
+
+    public Context() {
+        onState = new OnState(this);
+        offState = new OffState(this);
+        currentState = offState;
+    }
+
+    public void setCurrentState(State currentState) {
+        this.currentState = currentState;
+    }
+
+    public State getOffState() {
+        return offState;
+    }
+
+    public State getOnState() {
+        return onState;
+    }
+
+    public void on() {
+        currentState.on();
+    }
+
+    public void off() {
+        currentState.off();
+    }
+}

src/learn/simple_state/Main.java

@@ -0,0 +1,12 @@
+package learn.simple_state;
+
+public class Main {
+    public static void main(String[] args) {
+        Context context = new Context();
+        context.off();
+        context.off();
+        context.on();
+        context.on();
+        context.off();
+    }
+}

src/learn/simple_state/OffState.java

@@ -0,0 +1,20 @@
+package learn.simple_state;
+
+public class OffState implements State {
+    private Context context;
+
+    public OffState(Context context) {
+        this.context = context;
+    }
+
+    @Override
+    public void on() {
+        context.setCurrentState(context.getOnState());
+        System.out.println("Transition to on");
+    }
+
+    @Override
+    public void off() {
+        System.out.println("Already off");
+    }
+}

src/learn/simple_state/OnState.java

@@ -0,0 +1,20 @@
+package learn.simple_state;
+
+public class OnState implements State {
+    private Context context;
+
+    public OnState(Context context) {
+        this.context = context;
+    }
+
+    @Override
+    public void on() {
+        System.out.println("Already on");
+    }
+
+    @Override
+    public void off() {
+        context.setCurrentState(context.getOffState());
+        System.out.println("Transition to off");
+    }
+}

src/learn/simple_state/State.java

@@ -0,0 +1,6 @@
+package learn.simple_state;
+
+public interface State {
+    void on();
+    void off();
+}