Missing basic JavaDoc in Eclipse

Question

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

Answer 1

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).