It should create subdirectory "your_jarfilename" with the Maven's standard directory layout beneath it. Edit the Java files under your_jarfilename/src/main/java and JUnit tests under your_jarfilename/src/test/java (see JUnit tutorial on how to write JUnit tests at http://www.junit.org/index.htm ).
Compile, test and package (to a JAR file) is done with a single command in the "your_jarfilename" directory (i.e. the directory where pom.xml file is located):
If you want to make sure that "target" subdirectory is cleaned and everything is recompiled, then type