I like working with split editor windows when comparing code from 2 different sections of a file or different files. This is easy to do in Visual Studio (see here). It is just as easy in Eclipse too, though not obvious if you merely look through the menus.
[ To split a window, just grab hold of a tab and pull it to the side until it turns into a black arrow. ]
[ Leave it and it turns into a new window with a new tab group. ]
To have split windows with the same file: Choose Window → New Editor. That creates a new tab of the open file. Pull that tab as above to split the window.
For a horizontal split, pull the tab to the bottom of the window.
Keyboard shortcut for horizontal split:
Keyboard shortcut for vertical split:
Tried with: Eclipse Luna 4.4.1 and Ubuntu 14.04