complete all TODO sections in GasCar class

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

@@ -32,10 +32,10 @@ public abstract class Car extends Vehicle implements Serviceable {
     @Override
     public void showDetails() {
         System.out.println(
-                "brand: " + getBrand()
-                + " model: " + getModel()
-                + " year: " + getYear()
-                + " mileage: " + getMileage()
+                "brand: " + getBrand() + "\n"
+                + " model: " + getModel() + "\n"
+                + " year: " + getYear() + "\n"
+                + " mileage: " + getMileage() + "\n"
                 + " seats: " + getSeats()
         );
     }

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

@@ -1,15 +1,5 @@
 package org.model;
 
-/*
- * GasCar extends Car.
- * Inherits Serviceable from Car.
- *
- * Service logic for GasCar:
- * - needsService(): return true if mileage > 12000
- * - performService():
- *     Print "Engine oil changed"
- *     Reset fuelLevel to 100
- */
 
 import org.behavior.Refuelable;
 
@@ -27,13 +17,42 @@ public class GasCar extends Car implements Refuelable {
         this.fuelType = fuelType;
     }
 
-    // TODO: Override getEnergyType() → return fuelType + " (Gas)"
+    public double getFuelLevel() { return this.fuelLevel; }
+    public String getFuelType() { return this.fuelType; }
+    public void setFuelLevel(double fuelLevel) { this.fuelLevel = fuelLevel; }
 
-    // TODO: Implement refuel(double amount)
-    // Validate amount
-    // Cap at 100
+    @Override
+    public String getEnergyType() {
+        return getFuelType() + " (Gas)";
+    }
 
-    // TODO: Override showDetails()
-    // Call super.showDetails()
-    // Print fuel level and fuel type
+    @Override
+    public void refuel(double amount) {
+        if (amount < 0) {
+            throw new IllegalArgumentException("Amount must be positive");
+        }
+        if ( getFuelLevel() + amount > 100 ) {
+            setFuelLevel(100);
+        }
+        setFuelLevel(getFuelLevel() + amount);
+    }
+
+    @Override
+    public void showDetails() {
+        super.showDetails();
+        System.out.println(
+                "fuel level: " + this.fuelLevel + "\n"
+        + " fuel type: " + this.fuelType);
+    }
+
+    @Override
+    public boolean needsService(Vehicle v) {
+        return getMileage() > 12000;
+    }
+
+    @Override
+    public void performService() {
+        System.out.println("Engine oil changed");
+        setFuelLevel(100);
+    }
 }