Graphical Issue (Flickering Bar)

I was playing in fullscreen mode when I noticed a strange graphical bug. It seemed that a horizontal strip of the screen was flickering when my perspective moved, as if it was taking a moment to load. It occurs near the bottom of the screen, but above the health and hunger bar. It is not present within the menus. I tried restarting the game, but to no avail it remained. I do not know how to replicate this glitch, it happened randomly.

Update: When I hit "Save & Quit", the game crashed because "Java quit unexpectedly." This could be because I closed the Java control panel when the game was active (I was checking the version) while the game was open, but I doubt it.