Update Part 3.1 - Inheritance.md

Part 3.1 - Inheritance.md

@@ -81,13 +81,13 @@ interface Action {
     void do();
 }
 
-class Ask extends Action {
+class Ask implements Action {
     @Override void do() {
         new Scanner(System.in).next();
     }
 }
 
-class Print extends Action {
+class Print implements Action {
     @Override void do() {
         System.out.println("Hello");
     }