Can you configure the cursor in Eclipse to be a (possibly non-blinking) block, instead of a (blinking) bar?
I am running Xfce 4.10.
Short answer: no
From comments, OP clarified that the question was about Eclipse. The clue that the question was about the application's cursor (displayed as a part of the graphics within the window) rather than the desktop cursor was the comment about the blinking bar. Desktop cursor themes do not blink, and rarely are just a bar.
If Eclipse supported a change of cursor shape, that would be in one of the Preferences tabs, e.g., for the editor. OP does not find it there.
Web searches for the cursor shape in Eclipse only find comments that the shape is determined by whether you are in insert- or replace-mode. Seeing that, it appears that Eclipse does not allow this feature to be user-customized.
In a check with OSX, I see a feature in
as Use Custom Caret and Enable thick caret, which are both checked by default. But there is no check-box for blink.
As @Thomas Dickey has specified in his answer. No, there isn't. But, I have found a roundabout way of doing it on windows 10 and it works for me at least.
Doing this will disable eclipse's custom cursor and use the window's default. Thus, giving you the result that you desired(?).