How do I find a particular class from an Eclipse plug-in?

There are two easier approaches to adding Eclipse plug-ins to the Java search engine's index.
Option 1

In Eclipse 3.5 (Galileo) or later

Open the Plug-in Development Preference Page by going to Window > Preferences > Plug-in Development.
Check the box marked Include all plug-ins from target in Java search.

Option 2

Activate the 'Plug-ins' view by going to Window > Show View > Other > PDE > Plug-ins.
Select all plug-ins in the view.
From the context menu, select Add to Java Search.

Once you have done this, switch back to the Java perspective and use Navigate > Open Type (or press Ctrl + Shift + T) and start typing the name of the class or interface you are looking for. You will now be able to quickly open an editor
on any Java type in the Eclipse Platform.

同时配合plugin spy，可以快速定位source code.