As we all know, spam (unsolicited junk email) is clogging up the arteries of the internet. In this project you are going to modify the mail-system project from chapter 3 to filter spam. Here are the specifications for this
project. Read them carefully:

Do Exercise 3.33 if you haven't already (we did this in class). Modify the MailServer so that it uses a HashMap to store MailItems. The keys to the HashMap should be the names of the recipients, and each value should be an ArrayList containing all the MailItems stored for that recipient. Any email whose subject starts with the word "SPAM" or whose message contains the word "viagra" (capitalized or not) is spam, and should not be posted by the MailServer so that the intended recipient doesn't see it when he or she retrieves MailItems.

Add a method to the MailServer class called printAllMessages, that iterates through the users, prints out each user name, and prints out all the emails associated with that user.

Write unit tests that thoroughly test your modified mail-system. Make sure you test the case where you request mail for a user who has not yet received any mail.