Missing Javadoc in Eclipse for JRE 9

Question

Eclipse Oxygen.2 (4.7.2) fails to load standard javadoc when I select my JRE 9 install as default JRE.

Is that a bug?

When I switch back to JRE 8 it works.

EDIT

So, I was a bit short on that one, let me explain. When I select a JRE for Eclipse (Preferences > Java > Installed JREs), should it be a JRE9, a JDK9, a JRE8 or a JDK8 location, when I Edit it, I can see in the jrt-fs.jar (9) or in each separated jar including rt.jar (8) a Source attachment location (empty for JRE which is normal) and Javadoc location (official HTTP URL).

That's why I expect the Javadoc to display even with a JRE.

Now when I hover over a standard Java class, say java.io.IOException or java.lang.String for example:

• with JRE9 the Javadoc is not found in the tooltip
• with JDK9 it is found, but:
  • if I click "open attached Javadoc in browser" I get an Oracle NotFound error page looking for http://download.java.net/java/jdk9/docs/api/java/io/IOException.html which is the URL in the Javadoc Location of JRE9 & JDK9
  • if I click a link in the tooltip, eg java.io.InputStream , I get an Eclipse error: Exception:org.eclipse.jdt.core.JavaModelException: I/O exception which is Caused by: java.io.IOException: null , followed by a Java Model Exception: Java Model Status [C:\\Program Files\\Java\\jdk-9.0.4\\lib\\jrt-fs.jar\\java.base is not on its project's build path]
• with JRE8 or JDK8 the Javadoc is found in the tooltip as well as in the attached Javadoc in browser ( docs.oracle.com/javase/8/... )

So there are at least three problems:

• How come my tooltip doesn't work with JRE9? The possible duplicate question's answer says that Eclipse doesn't pull the tooltips from the javadoc location , so where does it pull it from?
  • [ANSWERED] from the source code if any. So I attached [jdk9_path]/lib/src.zip as Source Location in my JRE9 and it works.
• How come Eclipe is looking for jrt-fs.jar\\java.base , which does not exist?
  • [ANSWERED] I found the answer for that one: https://bugs.eclipse.org/bugs/show_bug.cgi?id=522054 still unsolved to this day.
• How come JDK9 & JRE9 come with an incorrect Javadoc Location ( http://download.java.net/java/jdk9/docs/api/ )?

Answer 1

JREs are the bare runtimes, they do not contain the compiler, packaging tools, sources, or documentation . The easiest solution is often to use a JDK instead.