There is a description of how the JDK was boostrapped on %%NetBSD%% [[https://docs.freebsd.org/cgi/getmsg.cgi?fetch=89377+0+/usr/local/www/mailindex/archive/2008/freebsd-java/20080203.freebsd-java|here]]. A description of using these to build the bootstrap-jdk for arm is available [[https://forums.freebsd.org/threads/47016/#post-266992|here]].