Just FYI, I verified that the build is ok for me on Windows 10 and Oracle 7 in top of 8 with a toolchain.
The build is also ok without a toolchain on OpenJDK 8 and 11. The build in not runnable on the current version of Java 15 or 16-EA since the 1.6 source level is no longer available (7 is the new minimum). Gary
