1

src/main/java/core/basesyntax/Car.java

@@ -1,25 +1,83 @@
 package core.basesyntax;
 
+import java.util.ArrayList;
 import java.util.List;
+import java.util.Objects;
 
-/**
- * Make this class immutable. See requirements in task description.
- */
-public class Car {
-    private int year;
-    private String color;
-    private List<Wheel> wheels;
-    private Engine engine;
+public final class Car {
+    private final int year;
+    private final String color;
+    private final List<Wheel> wheels;
+    private final Engine engine;
 
-    //implement this class
+    public Car(int year, String color, List<Wheel> wheels, Engine engine) {
+        this.year = year;
+        this.color = color;
+
+        this.wheels = new ArrayList<>();
+        if (wheels != null) {
+            for (Wheel w : wheels) {
+                this.wheels.add(new Wheel(w));
+            }
+        }
+
+        this.engine = engine == null ? null : new Engine(engine);
+    }
+
+    public int getYear() {
+        return year;
+    }
+
+    public String getColor() {
+        return color;
+    }
+
+    // ❗ MUST return COPY
+    public Engine getEngine() {
+        return engine == null ? null : new Engine(engine);
+    }
+
+    // ❗ MUST return COPY
+    public List<Wheel> getWheels() {
+        List<Wheel> copy = new ArrayList<>();
+        for (Wheel w : wheels) {
+            copy.add(new Wheel(w));
+        }
+        return copy;
+    }
+
+    // ❗ NO mutation → return new Car
+    public Car changeEngine(Engine engine) {
+        return new Car(year, color, wheels, engine);
+    }
+
+    public Car changeColor(String newColor) {
+        return new Car(year, newColor, wheels, engine);
+    }
+
+    public Car addWheel(Wheel newWheel) {
+        List<Wheel> newWheels = new ArrayList<>(wheels);
+        newWheels.add(new Wheel(newWheel));
+        return new Car(year, color, newWheels, engine);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (!(o instanceof Car)) {
+            return false;
+        }
+        Car car = (Car) o;
+        return year == car.year
+                && Objects.equals(color, car.color)
+                && Objects.equals(wheels, car.wheels)
+                && Objects.equals(engine, car.engine);
+    }
 
     @Override
-    public String toString() {
-        return "Car{"
-            + "year=" + year
-            + ", color='" + color + '\''
-            + ", wheels=" + wheels
-            + ", engine=" + engine
-            + '}';
+    public int hashCode() {
+        return Objects.hash(year, color, wheels, engine);
     }
 }

src/main/java/core/basesyntax/Engine.java

@@ -1,16 +1,44 @@
 package core.basesyntax;
 
-public class Engine {
-    private int horsePower;
-    private String manufacturer;
+import java.util.Objects;
 
-    //implement this class
+public final class Engine {
+    private final int horsePower;
+    private final String manufacturer;
+
+    public Engine(int horsePower, String manufacturer) {
+        this.horsePower = horsePower;
+        this.manufacturer = manufacturer;
+    }
+
+    public Engine(Engine other) {
+        this.horsePower = other.horsePower;
+        this.manufacturer = other.manufacturer;
+    }
+
+    public int getHorsePower() {
+        return horsePower;
+    }
+
+    public String getManufacturer() {
+        return manufacturer;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        Engine engine = (Engine) o;
+        return horsePower == engine.horsePower
+                && Objects.equals(manufacturer, engine.manufacturer);
+    }
 
     @Override
-    public String toString() {
-        return "Engine{"
-            + "horsePower=" + horsePower
-            + ", manufacturer='" + manufacturer + '\''
-            + '}';
+    public int hashCode() {
+        return Objects.hash(horsePower, manufacturer);
     }
 }

src/main/java/core/basesyntax/Wheel.java

@@ -1,14 +1,36 @@
 package core.basesyntax;
 
-public class Wheel {
-    private int radius;
+import java.util.Objects;
 
-    //implement this class
+public final class Wheel {
+    private final int radius;
+
+    public Wheel(int radius) {
+        this.radius = radius;
+    }
+
+    public Wheel(Wheel other) {
+        this.radius = other.radius;
+    }
+
+    public int getRadius() {
+        return radius;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        Wheel wheel = (Wheel) o;
+        return radius == wheel.radius;
+    }
 
     @Override
-    public String toString() {
-        return "Wheel{"
-            + "radius=" + radius
-            + '}';
+    public int hashCode() {
+        return Objects.hash(radius);
     }
 }