See these two images of eclipse project explorer below. The first one has dotted lines (so it’s much easier to see the hierarchy), while the second one does not (which is the case for the eclipse on my computer).
How to configure eclipse 3.6 on Windows 7 to display dotted lines?


Windows 7 removed this tree-view component from application usage, you can read about it here.
http://www.sevenforums.com/customization/25956-windows-explorer-tree-view-connecting-lines.html
In otherwords, you can’t add it back, but that link provides a modification which they claim helps out a bit.
It was called “Simple Folder View”, you can read about how it was turned on/off in Vista.
http://windows.microsoft.com/en-US/windows-vista/Change-folder-views-and-behavior