added lab4 ex1

src/lab4_command/ex1/Car.java

@@ -0,0 +1,16 @@
+package lab4_command.ex1;
+
+public class Car {
+    public void forward() {
+        System.out.println("Car goes forward");
+    }
+    public void backward() {
+        System.out.println("Car goes backward");
+    }
+    public void left() {
+        System.out.println("Car goes left");
+    }
+    public void right() {
+        System.out.println("Car goes right");
+    }
+}

src/lab4_command/ex1/CarCommand.java

@@ -0,0 +1,10 @@
+package lab4_command.ex1;
+
+public abstract class CarCommand {
+    protected Car car;
+    public CarCommand(Car car) {
+        this.car = car;
+    }
+    public abstract void execute();
+    public abstract void undo();
+}

src/lab4_command/ex1/Game.java

@@ -0,0 +1,38 @@
+package lab4_command.ex1;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Stack;
+
+public class Game {
+    private final Map<Integer, CarCommand> actions = new HashMap<>();
+    private final Stack<CarCommand> history = new Stack<>();
+    public Car car;
+
+    public Game() {
+        car = new Car();
+    }
+
+    public void bindKey(int key, CarCommand command) {
+        actions.put(key, command);
+    }
+
+    public void unbindKey(int key) {
+        actions.remove(key);
+    }
+
+    public void pushKey(int key) {
+        if (actions.containsKey(key)) {
+            CarCommand action = actions.get(key);
+            action.execute();
+            history.push(action);
+        }
+    }
+
+    public void undo() {
+        if (history.empty()) {
+            return;
+        }
+        history.pop().undo();
+    }
+}

src/lab4_command/ex1/MobilePhone.java

@@ -0,0 +1,25 @@
+package lab4_command.ex1;
+
+import lab4_command.ex1.commands.BackwardCommand;
+import lab4_command.ex1.commands.ForwardCommand;
+import lab4_command.ex1.commands.LeftCommand;
+import lab4_command.ex1.commands.RightCommand;
+
+public class MobilePhone {
+    public static void main(String[] args) {
+        Game game = new Game();
+
+        game.bindKey(0, new ForwardCommand(game.car));
+        game.bindKey(1, new BackwardCommand(game.car));
+        game.bindKey(2, new LeftCommand(game.car));
+        game.bindKey(3, new RightCommand(game.car));
+
+        game.pushKey(2);
+        game.pushKey(2);
+        game.pushKey(3);
+        game.pushKey(2);
+        game.pushKey(0);
+        game.pushKey(1);
+        game.undo();
+    }
+}

src/lab4_command/ex1/commands/BackwardCommand.java

@@ -0,0 +1,20 @@
+package lab4_command.ex1.commands;
+
+import lab4_command.ex1.Car;
+import lab4_command.ex1.CarCommand;
+
+public class BackwardCommand extends CarCommand {
+    public BackwardCommand(Car car) {
+        super(car);
+    }
+
+    @Override
+    public void execute() {
+        car.backward();
+    }
+
+    @Override
+    public void undo() {
+        car.forward();
+    }
+}

src/lab4_command/ex1/commands/ForwardCommand.java

@@ -0,0 +1,20 @@
+package lab4_command.ex1.commands;
+
+import lab4_command.ex1.Car;
+import lab4_command.ex1.CarCommand;
+
+public class ForwardCommand extends CarCommand {
+    public ForwardCommand(Car car) {
+        super(car);
+    }
+
+    @Override
+    public void execute() {
+        car.forward();
+    }
+
+    @Override
+    public void undo() {
+        car.backward();
+    }
+}

src/lab4_command/ex1/commands/LeftCommand.java

@@ -0,0 +1,20 @@
+package lab4_command.ex1.commands;
+
+import lab4_command.ex1.Car;
+import lab4_command.ex1.CarCommand;
+
+public class LeftCommand extends CarCommand {
+    public LeftCommand(Car car) {
+        super(car);
+    }
+
+    @Override
+    public void execute() {
+        car.left();
+    }
+
+    @Override
+    public void undo() {
+        car.right();
+    }
+}

src/lab4_command/ex1/commands/RightCommand.java

@@ -0,0 +1,20 @@
+package lab4_command.ex1.commands;
+
+import lab4_command.ex1.Car;
+import lab4_command.ex1.CarCommand;
+
+public class RightCommand extends CarCommand {
+    public RightCommand(Car car) {
+        super(car);
+    }
+
+    @Override
+    public void execute() {
+        car.right();
+    }
+
+    @Override
+    public void undo() {
+        car.left();
+    }
+}