Class GasCar completed.

src/main/java/org/model/Car.java

@@ -21,10 +21,10 @@ public abstract class Car extends Vehicle implements Serviceable {
         this.seats = seats;
     }
 
-    //Override
+    @Override
     abstract String getEnergyType();
 
-    //Override
+    @Override
     public void showDetails() {
         System.out.println(getBrand());
         System.out.println(getModel());

src/main/java/org/model/GasCar.java

@@ -27,13 +27,37 @@ public class GasCar extends Car implements Refuelable {
         this.fuelType = fuelType;
     }
 
-    // TODO: Override getEnergyType() → return fuelType + " (Gas)"
+    @Override
+    public String getEnergyType() {
+        return (fuelType + " (Gas)");
+    }
 
-    // TODO: Implement refuel(double amount)
-    // Validate amount
-    // Cap at 100
+    //Implement Refuelable
+    public void refuel(double amount) {
+        if (amount <= 0) {
+            System.out.println("Invalid amount!");
+            return;
+        }
+        if (fuelLevel + amount > 100) {System.out.println("Invalid amount!");}
+        else {System.out.println("Refuelable!");}
+    }
 
-    // TODO: Override showDetails()
-    // Call super.showDetails()
-    // Print fuel level and fuel type
+    @Override
+    public void showDetails() {
+        super.showDetails();
+        System.out.println(fuelLevel);
+        System.out.println(fuelType);
+    }
+
+    @Override
+    public boolean needsService(Vehicle v) {
+        double mileage = v.getMileage();
+        return (mileage > 12000);
+    }
+
+    @Override
+    public void performService() {
+        System.out.println("Engine oil changed");
+        fuelLevel = 100;
+    }
 }