complete GasCar class

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

@@ -27,13 +27,49 @@ 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
+    public void refuel(double amount)
+    {
+        if (amount < 0)
+        {
+            System.out.println("Cannot refuel negative amount!");
+            return;
+        }
+        this.fuelLevel += amount;
+        if (this.fuelLevel > 100)
+        {
+            this.fuelLevel = 100;
+        }
+        System.out.println("Refueled. Current fuel level: " + this.fuelLevel);
+    }
+
+    @Override
+    public void showDetails()
+    {
+        super.showDetails();
+        System.out.println("fuel type: " + this.fuelType + " | fuel level: " + this.fuelLevel);
+    }
+
+    @Override
+    public boolean needsService(Vehicle v)
+    {
+        if (v.getMileage() > 12000)
+        {
+            return true;
+        }
+        return false;
+    }
+
+    @Override
+    public void performService()
+    {
+        System.out.println("Engine oil changed");
+        this.fuelLevel = 100;
+    }
 
-    // TODO: Override showDetails()
-    // Call super.showDetails()
-    // Print fuel level and fuel type
 }