Add toString method to allow easy printing.
Array-based version of the PersonQueue, ...
based on the ArrayStringStack implementation given in example code
uses ArrayPersonQueue of the...     Test output->
...PersonQueue interface. includes main method that does a basic test
adding ten people to the queue and then "serving" them.

-> Test output looks good to me:

$ java Supermarket
Testing SuperMarket, today people arrive at the till in alphabetical order!
Add ten people to the queue:
Adding Adam Ant
Adding Bill Bailey
Adding Charlie Chalk
Adding Dan Dare
Adding Eddy Eagle
Adding Franky Fox
Adding Gary Glitter
Adding Henry Hippo
Adding Inky Ian
Adding Jane Jenkin
Now serve a single customer: Adam Ant is 44 years old
Now serve another customer: Bill Bailey is 11 years old
Adding another customer Kevin
Serve the complete queue:
Serve person Charlie Chalk is 13 years old
Serve person Dan Dare is 23 years old
Serve person Eddy Eagle is 87 years old
Serve person Franky Fox is 5 years old
Serve person Gary Glitter is 63 years old
Serve person Henry Hippo is 105 years old
Serve person Inky Ian is 88 years old
Serve person Jane Jenkin is 30 years old
Serve person Kevin Keegan is 65 years old