The c++_example and java_example directories provided in capture.zip contain sample players implemented in C++ and java. The source code for these will demonstrate how a player is to interact with the game, and they may give you some ideas about how your own player could operate. You can compile these independently and then run them against each other in the game using a command like the following:
java -jar capture.jar -player exe c++_example/march -player java java_example.Eight
Source code for the java is stored in a java_example subdirectory and is given a matching package name. Keep in mind that submitted players implemented in Java cannot be organized this way; they must be defined in the default package. The Java example has been organized this way only to simplify distribution.