polymorphism completed

java/inheritance/Program.java

@@ -1,9 +1,14 @@
 public class Program {
   public static void main(String[] args) {
-    Dog d = new Dog("buster");
-    Cat c = new Cat("mittens");
+    // because cat and dog are subclasses of animal, they can be stored in an array of animals
+    Animal[] animals = { 
+      new Dog("buster"), 
+      new Cat("mittens") 
+    };
 
-    d.make_sound();
-    c.make_sound();
+    for (Animal a : animals) {
+      // when calling the make_sound function, the implementation of the actual class gets called (in this case cat or dog)
+      a.make_sound();
+    }
   }
 }

java/inheritance/README.md

@@ -2,7 +2,6 @@
 
 Relevant files:
 
-- [Program.java](./Program.java)
 - [Animal.java](./Animal.java)
 - [Cat.java](./Cat.java)
 - [Dog.java](./Dog.java)