The crossing task for PRO3 is an exercise in using executors.
The description in crossingtask_en.pdf, the source code to start with in pro3_crossing.zip.
Before you can use this poject you must learn Netbeans about the library crossingui. To do that you should pick up a copy of crossinggui.jar, store it in the java lib directory (/usr/share/java on linux, make your own convention under Windows) and set the library in netbeans→tools→libraries→new library. as in the image.
To start with the task, you may then unzip the pro3_crossing.zip and open the project in netbeans.
Note that this project will build, but won't work.
You can get an idea of what the multilane solution looks like by starting the jar
with java -cp crossinggui.jar crossing.gui.GuiDemo.
Task
You should find a solution to make this crossing safe for all kind of crossing configurations by using the new concurrency classes, especially the executor framework.
Hint: as a first step try to make the crossing safe in case there is only one lane at each corner, the so called monolane crossing.
The javadoc api documentation of the crossing can be found here too.