The Jasclipse plugin helps you to navigate in your *.j file by providing an Outline view for it
To open an Outline view, select Window -> Show View -> Outline
Outline tree for *.j file contains its source file, class name, super class, implemented interfaces and all fields and methods. It also includes labels.
You can navigate your *.j file simply by clicking any node in Outline tree. Editor will focus to the part in *.j file corresponding with selected node.