Imagine a pile of books on your desk. Each book is so large and heavy that you can remove only the top one from the pile. You cannot remove a book from under another one. Likewise, you can add another...

Imagine a pile of books on your desk. Each book is so large and heavy that you can remove only the top one from the pile. You cannot remove a book from under another one. Likewise, you can add another book to the pile only by placing it on the top of the pile. You cannot add a book beneath another one. If you represent books by their titles alone, design and implement a class PileOfBooks that you can use to track the books in the pile on your desk.