implemented add methods and made Car class immutable

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

@@ -1,17 +1,62 @@
 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 = wheelsCopy(wheels);
+        this.engine = (engine == null) ? null : engine.clone();
+    }
+
+    public List<Wheel> wheelsCopy(List<Wheel> wheels) {
+        List<Wheel> wheelsCopy = new ArrayList<>(wheels.size());
+        for (Wheel wheel : wheels) {
+            wheelsCopy.add(wheel.clone());
+        }
+        return wheelsCopy;
+    }
+
+    public Car changeEngine(Engine engine) {
+        return new Car(this.year, this.color, this.wheels, engine);
+    }
+
+    public Car changeColor(String newColor) {
+        return new Car(this.year, newColor, this.wheels, this.engine);
+    }
+
+    public Car addWheel(Wheel newWheel) {
+        List<Wheel> wheelsCopy = wheelsCopy(this.wheels);
+        wheelsCopy.add(newWheel);
+        return new Car(this.year, this.color, wheelsCopy, this.engine);
+    }
+
+    public int getYear() {
+        return year;
+    }
+
+    public String getColor() {
+        return color;
+    }
+
+    public List<Wheel> getWheels() {
+        return wheelsCopy(this.wheels);
+    }
+
+    public Engine getEngine() {
+        return (engine == null) ? null : engine.clone();
+    }
 
     @Override
     public String toString() {
@@ -22,4 +67,21 @@ public String toString() {
             + ", engine=" + engine
             + '}';
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        Car car = (Car) o;
+        return getYear() == car.getYear()
+                && Objects.equals(getColor(), car.getColor())
+                && Objects.equals(getWheels(), car.getWheels())
+                && Objects.equals(getEngine(), car.getEngine());
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(getYear(), getColor(), getWheels(), getEngine());
+    }
 }

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

@@ -1,16 +1,61 @@
 package core.basesyntax;
 
-public class Engine {
+import java.util.Objects;
+
+public class Engine implements Cloneable {
     private int horsePower;
     private String manufacturer;
 
-    //implement this class
+    public Engine(int horsePower, String manufacturer) {
+        this.horsePower = horsePower;
+        this.manufacturer = manufacturer;
+    }
+
+    public int getHorsePower() {
+        return horsePower;
+    }
+
+    public void setHorsePower(int horsePower) {
+        this.horsePower = horsePower;
+    }
+
+    public String getManufacturer() {
+        return manufacturer;
+    }
+
+    public void setManufacturer(String manufacturer) {
+        this.manufacturer = manufacturer;
+    }
 
     @Override
     public String toString() {
         return "Engine{"
-            + "horsePower=" + horsePower
-            + ", manufacturer='" + manufacturer + '\''
-            + '}';
+                + "horsePower=" + horsePower
+                + ", manufacturer='" + manufacturer + '\''
+                + '}';
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        Engine engine = (Engine) o;
+        return horsePower == engine.horsePower
+                && Objects.equals(manufacturer, engine.manufacturer);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(horsePower, manufacturer);
+    }
+
+    @Override
+    public Engine clone() {
+        try {
+            return (Engine) super.clone();
+        } catch (CloneNotSupportedException e) {
+            throw new RuntimeException("Can't create clone for Engine object", e);
+        }
     }
 }

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

@@ -1,14 +1,49 @@
 package core.basesyntax;
 
-public class Wheel {
+import java.util.Objects;
+
+public class Wheel implements Cloneable {
     private int radius;
 
-    //implement this class
+    public Wheel(int radius) {
+        this.radius = radius;
+    }
+
+    public int getRadius() {
+        return radius;
+    }
+
+    public void setRadius(int radius) {
+        this.radius = radius;
+    }
 
     @Override
     public String toString() {
         return "Wheel{"
             + "radius=" + radius
             + '}';
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        Wheel wheel = (Wheel) o;
+        return radius == wheel.radius;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(radius);
+    }
+
+    @Override
+    public Wheel clone() {
+        try {
+            return (Wheel) super.clone();
+        } catch (CloneNotSupportedException e) {
+            throw new RuntimeException("Can't create clone for Wheel object", e);
+        }
+    }
 }