added updateFuelLevel routines, changed fuelLevel from float to double

SelfDrivingCar.java

@@ -1,6 +1,6 @@
 public class SelfDrivingCar {
     private int speed;
-    private int fuelLevel;
+    private double fuelLevel;
     public static void main(String[] args) {
     }
 
@@ -21,7 +21,8 @@ public class SelfDrivingCar {
     }
 
     public void updateFuelLevel() {
-        
+        //would check fuel sensor and update accordingly
+        fuelLevel = 0.75;
     }
 
     public void changeDirection() {