Complete VMS with polymorphism demonstration

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

@@ -27,13 +27,47 @@ 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("Error");
+            return;
+        }
 
-    // TODO: Override showDetails()
-    // Call super.showDetails()
-    // Print fuel level and fuel type
+        if (this.fuelLevel + amount > 100) {
+            this.fuelLevel = 100;
+        } else {
+            this.fuelLevel += amount;
+        }
+    }
+
+    @Override
+    public void showDetails() {
+        super.showDetails();
+        System.out.print(
+                " | fuel type: " + fuelType +
+                " | fuel level: " + fuelLevel
+        );
+        System.out.println();
+    }
+
+    @Override
+    public boolean needsService(Vehicle v) {
+        if(getMileage() > 12000) {
+            return true;
+        }
+        else {
+            return false;
+        }
+    }
+
+    @Override
+    public void performService() {
+        System.out.println("Engine oil changed");
+        this.fuelLevel = 100;
+    }
 }