Your company is doing some data cleanup, and notices that the email list of all users has been getting outdated. For one, there are some users with repeat email addresses, and some of the email accounts no longer exist. Your job is to create a series of methods that can purge some of the old data from the existing email list.

Create static methods in the DataPurge class that can do the following:

Test your methods out in the DataPurgeTester file. You don’t have to change anything there, but the methods should work accordingly!