The following navigation, activation and selection keyboard bindings on JSplitPane need to be implemented for proper operation and key binding sequences. 

JSplitPane:
                Navigate in - Tab
               Navigate out - Ctrl+Tab, Ctrl+Shift+Tab
           Navigate between - Tab, F6 (last element with focus regains
                                       focus when its pane is moved to,
                                       F6 provides CUA compliance)
    Give focus splitter bar - F8
 Remove focus from splitter - F8, Tab
                Change size - Arrow keys, home, and end
                              (moves the pane splitter appropriately)

Usability:
- A JSplitPane is considered to have focus as soon as one of its child components has the focus.
- F8 while the JSplitPane has the focus (one of its child components is in focus) gives the divider (splitter, split bar) the focus and allows to move it around with the cursor keys. This resize mode is ended by either another (F8 | Tab) where the focus goes to the next component in the JSplitPane, or by (Ctrl+Tab | Ctrl+Shift+Tab) where the focus goes to the next component outside of the JSplitPane.

Note:
The only split pane I found was on dtmail and there was no ability provided to jump directly between panes. You started in one pane then navigate to all things in between, including the change size bar, then finally end up in the second split pane window.