How do I get the packages contained in a jar/library/dependency?

If you want to display it as a Node you can use:

org.netbeans.spi.java.project.support.ui.PackageView.createPackageView().

If you need just a list of packages it can be obtained by

ClassIndex.getPackageNames()

for jars which were scanned by indexing.

— provided by Tomas Zezula

Apache NetBeans 23