To run Jmap using just the .jar file:
java -jar jmap.jar
(or double-click on the jmap.jar) You will need the Java Runtime Environment installed.

To compile you will need the Java Standard Development Kit:
javac *.java
Then:
jar -cvmf manifest.txt jmap.jar *.class ports.defs
or
java JMapFE

It’s been a while since I did any work on the project. It was written for Java 1.3 when I was a student, hope it may still be useful and apologies if the code quality isn’t what it should be – it was just a quick project for fun.

If I remember correctly, the GUI is contained within the JavaFE class. Scanning is multi-threaded, with many hosts and many ports being scanned simultaneously. The results of each individual scan is passed to the main thread using the Observable mechanism.