This program is a practice exercise for superclass and subclass, and it must be written in 1 java file named "Person." The output of the code is supposed to display the messages "This is the doctor class" and "This is the person class," but when I run the code, there are no messages, and the output is empty. There are no error messages either, so I'm not sure what's wrong with the code. Could someone fix my code, compile it, show me a screenshot of the output, and explain what was wrong with my program and what changes you've made?