add example of ovverriding and calling super on a overridden method

Author: Pietro Di Bello

src/it/bemyeye/learn/subclass/override/example/Car.java

@@ -0,0 +1,20 @@
+package it.bemyeye.learn.subclass.override.example;
+
+class Car {
+    int cylinders;
+    int currentSpeed;
+
+    public Car(int cylinders) {
+        this.cylinders = cylinders;
+        this.currentSpeed = 0;
+    }
+
+    void accelerate(int speedGain) {
+        currentSpeed += speedGain;
+    }
+
+    public Double calcolaBollo() {
+        return cylinders * 0.75;
+    }
+
+}

src/it/bemyeye/learn/subclass/override/example/CarTest.java

@@ -0,0 +1,17 @@
+package it.bemyeye.learn.subclass.override.example;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class CarTest {
+
+    @Test
+    public void calcolaBolloDipendeDallaCilindrata() {
+        Car car = new Car(1000);
+        assertEquals(750.0, car.calcolaBollo(), 0);
+
+        Suv suv = new Suv(1000);
+        assertEquals(1500.0, suv.calcolaBollo(), 0);
+    }
+}

src/it/bemyeye/learn/subclass/override/example/Suv.java

@@ -0,0 +1,13 @@
+package it.bemyeye.learn.subclass.override.example;
+
+class Suv extends Car {
+
+    public Suv(int cylinders) {
+        super(cylinders);
+    }
+
+    @Override
+    public Double calcolaBollo() {
+        return super.calcolaBollo() * 2;
+    }
+}