How to get Javadocs for Eclipse DOM plug-in development classes?

I am writing a plug-in for Java in Eclipse that utilizes the Eclipse DOM classes. I would like to see Javadocs for these classes but I am unable to do so. For example, when I request javadocs for the method recordModifications() in class org.eclipse.jdt.core.dom.CompilationUnit, I get a message that s开发者_如何学运维ays:

The documentation location for 'recordModifications()' has not been configured. For elements from libraries specify the Javadoc location URL on the properties page of the parent JAR ('/Applications/eclipse/plugins/org.eclipse.jdt.core_3.6.1.v_A68_R36x.jar').

However, when I go to the properities for the JAR, it says:

Javadoc location. The current class path entry belongs to container 'Plug-in Dependencies' which does not allow user modifications to Javadoc locations on its entires.

Any advice?

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I think what you should do is install the eclipse sources.
do it by Help->Install new software...-> select Eclipse project updates update site. select eclipse plugin developer resources.
the sources suppose to be there.
from the sources you will be able to see also javadocs.