Up to a few days ago, Eclipse was working fine in locating the javadoc for base classes such as Java.io.File. Recently, though, hovering over these classes only yields a message indicating that the source and javadoc are missing:
"Note: This element has no attached source and the Javadoc could not be found in the attached Javadoc."
I couldn't for the life of me locate the option that would let me reselect the location of the basic documentation. Does anyone know how to fix this?
Expand your JRE System library and find rt.jar (classes.jar for Mac OS X). Right click, and select 'Properties'.
You can then specify the Javadoc location (as well as the source location).
rt on windows. An edit to the image with the text "rt.jar on windows" would be nic - Old Badman Grey 2014-11-11 19:18
Additionally, all my other JARs are already pointing to http://docs.oracle.com/javase/7/docs/api/ including rt.ja - anon58192932 2014-11-18 02:31
The best way to do it is
Go to Project > Properties > Java Build Path > Libraries and expand JRE System Library [your jre version] then, rt.jar. Select Source attachment, click Edit…. Select the source code file (External File…) and press OK.
Other ways to attach java source code is mentioned in this link
http://www.cavdar.net/2008/07/14/3-ways-of-jdk-source-code-attachment-in-eclipse/
Javadoc Location at jrt-fs.jar, and set https://docs.oracle.com/javase/7/docs/api/. This finally works for "Eclipse Oxygen.2" and "JavaSE-9 (jre-9.0.4) - Brethlosze 2018-03-09 20:25
I encountered this problem now a couple of times too. It's especially annoying if you have a lot of projects in your workspace and you don't want to set the javadoc locations for each project.
Referencing the online documentation works well indeed, and there is a way to do that globally for all Java libraries:
http://docs.oracle.com/javase/8/docs/api/. (If you press ''Validate...'' it will tell you if it is a valid javadoc location.)And here you have some images:
And your basic Java javadoc is ready to go.
Additionally, I can successfully query http://docs.oracle.com/javase/7/docs/api/ from a browser. This is for Open JDK 7 on Ubuntu 14.04 - anon58192932 2014-11-18 02:41
Press ctrl+click (or command+click if you're on a Mac) on any method which doesn't have javadocs. For example, in this line:
System.out.println();
... assuming that no javadocs are available for println, control-clicking on println will open a new tab with a button labeled "Attach Source...". And that's it!
I had the same problem.
I uninstalled eclipse, removed all eclipse specific data from my user's home- and application data directory, uninstalled all Java JREs and JDKs but nothing helped.
The solution on my system was to change the protocol in the JavaDoc URL from HTTP to HTTPS
e.g. for JRE 7 i changed the URL from http://docs.oracle.com/javase/7/docs/api/ to https://docs.oracle.com/javase/7/docs/api/
(use the steps mentioned by Terry and replace the 'http' with 'https')