This requires Play Framework 1.2.x. The latest version is available from

http://downloads.typesafe.com/play/1.2.7/play-1.2.7.zip

Installation instructions are at:

http://www.playframework.com/documentation/1.2.7/install

To Build, run the dependencies command:

play deps

Then (due to a bug in Guice module) please delete the generated directory at:

$APP_PATH/modules/guice-1.2/test

Start play in test mode:

play test

Then go to

http://localhost:9000/@tests

and click "Run all"

to stop play server.

Start play:

play run

To view the answers to the tests, go to

http://localhost:9000/

to stop play server.

Count of the matches for a particular gender is retrieved issuing the following request:

GET /demographic/gender/count/{gender}

where {gender} is male or female. Response will be JSON object with single property of 'count' containing the resulting value.

Name of the individual with the greatest age retrieved issuing the following request:

GET	/demographic/age/maximum

Response will be JSON object with single property of 'name' containing the name of the person matching the search.

Difference in the ages between two :

GET		/demographic/age/compare/{lowName},{highName}

where {lowName} is name (or part) for the younger individual and {highName} is name (or part) for the older individual. A comma separator is used to indicate order-sensitive scoping information, as recommended by Sam Ruby (RESTful Web Services, p.119)

Response will be JSON object with single property of 'days' containing the resulting difference. If the second person is younger, the value will be negative. If this scoping data is invalid, a 400 response will be sent, with a description of the error in the errorMessage field of the JSON response body.

Although TDD and tests were not mentioned in the requirements, I have written it as a test-driven project.

I have recently been interested by Cory Maksymchuk's talk "3 Patterns for Cleaner Code" - http://www.infoq.com/presentations/3-Patterns-Cleaner-Code. This describes how separating an algorithm applied to a collection from the loop code can make testing the algorithm much easier. Google Guava has implementations that are very similar to those described by Cory, so I decided to try it out for this project.

I am aware that Guava documentation counsels against overusing functional approaches within Java versions before 8 (see 'Caveats' in http://code.google.com/p/guava-libraries/wiki/FunctionalExplained) but for this code I was looking to place testability over simplicity.

Given the simplicity of the predicate algorithms in this case, it probably didn't allow any significant improvement in testability.

I've also been wanting to have a look at Joda-Time for quite a long time, and was aware it had useful date interval capabilities.

Play framework was chosen because of ease with which the RESTful APIs could be created, and because it easily integrates with Guice to allow annotation-driven DI. Version 1 was chosen for familiarity and because some users have reported Java to be a 2nd-class citizen within Version 2.