macOS – Installing Java OpenJDK 8 on High Sierra or Newer Versions

It seems I found a source of precompiled OpenJDK:
http://code.google.com/p/openjdk-osx-build/
The OpenJDK 7 builds there are universal, and do indeed run in 32bit mode. The latest version is 7u6, which is not quite as recent as the 7u7 available from Oracle, but should be recent enough for my requirements.

Alas, my original problem persists, so I might have to compile my JVM myself after all. I found there is a jdk7u-osx repository in the OpenJDK mercurial repositories, and its README-builds file provides reasonable instructions on how to build stuff. The part about source drops appears particularly important. I still have some troubles, but those seem to be bugs in the build process or similar, so I'll take them up with the macosx-port-dev mailing list.

From replies to a question I asked on Apple's java-dev list it would appear that on a Mac with Java 8 from Oracle installed, but not Java 6 from Apple, there is no current way to open a Java application bundle that was created using Apple's own old jar bundler technology. I suspect this is because the JavaApplicationStub is written to expect some aspect of Apple's Java not present in Oracle's Java.

From a user's point of view the only thing to do would seem to be to download and install Java 6 from https://support.apple.com/kb/DL1572 while it is still available.

From a developer's point of view the safest bet would be to embed Java within one's application bundle using a tool such as jwrapper (www.jwrapper.com). Alternatively there may be tools for creating a bundle that will run with Oracle's Java 8+.