complete all TODO sections in Vehicle class

src/main/java/org/model/Vehicle.java

@@ -1,10 +1,5 @@
 package org.model;
 
-/*
- * Abstract base class for all vehicles.
- * This class DOES NOT implement Serviceable.
- * Service behavior will be defined in concrete subclasses.
- */
 
 public abstract class Vehicle {
 
@@ -20,13 +15,18 @@ public abstract class Vehicle {
         this.mileage = mileage;
     }
 
-    // TODO: Create getters for all fields
+    public String getBrand() { return this.brand; }
+    public String getModel() { return this.model; }
+    public int getYear() { return this.year; }
+    public double getMileage() { return this.mileage; }
 
-    // TODO: Implement addMileage(double km)
-    // If km is negative → print error
-    // Otherwise increase mileage
+    public void addMileage(double mileage) {
+        if (mileage < 0) {
+            throw new IllegalArgumentException("Mileage cannot be negative");
+        }
+        this.mileage += mileage;
+    }
 
-    // TODO: Declare abstract method getEnergyType()
 
     public void basicInfo() {
         System.out.println(
@@ -37,4 +37,5 @@ public abstract class Vehicle {
     }
 
     public abstract void showDetails();
+    public abstract String getEnergyType();
 }