The easy way to start is to launch the skel.build.xml:
> ant -f skel.build.xml

This will start a wizard which will generate a skeleton for a java project
that has a suite of targets it knows how to execute.

Examples of targets the generated build.xml will provide:
 * checkstyle.report.html Generates an HTML report of static code analysis (Checkstyle).
 * compile Compile your code
 * dist Build a jar file with the built classes, resources
 * docs Build the Javadocs
 * junit.report.html Run the JUnit Test Suite (defined in the property junit.testsuite.class)

If you have an existing project, try using migrate.build.xml:
> ant -f migrate.build.xml