Old post forgotten back in June/July with included link to the download.
For some reason Adobe Illustrator CS6 (and older) and probably some other applications from Adobe require the legacy Java 6 runtime to even start on OS X (except if one wants to do some hacks to make newer versions of Java from Oracle work). For the ones not loaded with cash there’s good news: Apple extended the support for their old Java 6 and released Java for OS X 2015-001 back in July, 2015 which allows OS X 10.11 El Capitan users to run Adobe Illustrator CS6 without a glitch (I haven’t experienced any yet).
Java for OS X 2015-001 can be downloaded from: https://support.apple.com/kb/DL1572
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