add inheritance example

src/encapsulationInheritancePolymorphism/inheritance/ElectricEngine.java

@@ -0,0 +1,5 @@
+package encapsulationInheritancePolymorphism.inheritance;
+
+public class ElectricEngine extends Engine {
+    private String batteryType;
+}

src/encapsulationInheritancePolymorphism/inheritance/Engine.java

@@ -0,0 +1,5 @@
+package encapsulationInheritancePolymorphism.inheritance;
+
+public class Engine {
+    private int power;
+}

src/encapsulationInheritancePolymorphism/inheritance/Main.java

@@ -0,0 +1,7 @@
+package encapsulationInheritancePolymorphism.inheritance;
+
+public class Main {
+    public static void main(String[] args) {
+        ElectricEngine electricEngine = new ElectricEngine();
+    }
+}