At the moment this book was being written there were two implementations of TAP for Java: JTap and tap4j.

JTap is a port of libtap (Perl) to Java by Patrick LeBoutillier (patl@cpan.org). It is the oldest implementation of the protocol to Java, however it doesn't outputs TAP, i.e. JTap is only a producer, not a consumer.

tap4j was created in 2010 by Bruno P. Kinoshita. It contains both a consumer and a producer in Java. The current version of tap4j is 2.0 and it is already deployed to Maven central repository. What is interesting is that the author of tap4 contacted JTap's author and after some talk Patrick sent metatap to Bruno. Using this Perl script you can say what you expect (2 success test results and 1 that failed) and it will check if a given TAP Stream is according to what you are expecting.

The current parser of tap4j is a Regular Expressions parser. The tap4j team is using snakeyaml parser as basis to write a recursive descent parser. And the team also has plans of submitting tap4j to Apache Incubator.

tap4j is low level API. You can use it directly or abstract TAP and plug it with JUnit or TestNG test frameworks. Both APIs contain extension points that let you extend its functionality. tap4j contains extensions for both test frameworks.