This page, for the JDK 8 javadoc tool, does not list correct values for the -source option https://docs.oracle.com/javase/8/docs/technotes/tools/unix/javadoc.html#CHDBGDFI It lists 1,3, 1.4, 1.5, but not 6, 7, 8. (The page for JDK 9 does list correct values.)