diff --git a/src/com/in28minutes/java/oops/inheritance/InheritanceExamples.java b/src/com/in28minutes/java/oops/inheritance/InheritanceExamples.java
index ba2134a..43f58e2 100644
--- a/src/com/in28minutes/java/oops/inheritance/InheritanceExamples.java
+++ b/src/com/in28minutes/java/oops/inheritance/InheritanceExamples.java
@@ -23,5 +23,7 @@ public class InheritanceExamples {
 	public static void main(String[] args) {
 		Animal animal = new Cat();
 		System.out.println(animal.bark());
+		animal = new Dog();
+		System.out.println(animal.bark());
 	}
 }
diff --git a/src/com/in28minutes/java/oops/interfaces/InterfaceExamples.java b/src/com/in28minutes/java/oops/interfaces/InterfaceExamples.java
index aa24355..36d585d 100644
--- a/src/com/in28minutes/java/oops/interfaces/InterfaceExamples.java
+++ b/src/com/in28minutes/java/oops/interfaces/InterfaceExamples.java
@@ -1,6 +1,7 @@
 package com.in28minutes.java.oops.interfaces;
 
 interface Flyable {
+	final int max_altitude=3000;	//data members are final in interfaces
 	void fly();
 }
 
@@ -20,5 +21,6 @@ public class InterfaceExamples {
 	public static void main(String[] args) {
 		Flyable flyable = new Bird();
 		flyable.fly();
+		System.out.println(flyable.max_altitude);
 	}
 }