Java was released under the slogan 'write once, run anywhere'; while its adoption was probably more about 'now we have a language that provides garbage collection in a familiar workflow and with a good standard library', as far as Sun's management was concerned, it was an anti-Microsoft weapon, and to this end, it tried to pave over differences between platforms.
One category of differences was in floating-point arithmetic. IEEE 754 made some progress towards reproducible floating point, but still left a great deal of variation. Java tried to nail it down. This was a controversial move. William Kahan wrote an impassioned rant about it; as it happens, I mostly agree with the Java designers and mostly disagree with Kahan, but his writing is always thought-provoking.
Now I vaguely remember the Java decision mostly held up, and to this day floating point in Java is mostly reproducible, but there was one issue, one small aspect of floating-point arithmetic, on which they backed down, one edge case in which platform differences in floating-point hardware can still manifest. But I cannot for the life of me remember what that was.
What was the aspect of floating point on which a later version of Java backed down?