For the past couple of years, I've been developing a Java Swing application-- basically a vector graphics program. I've been working on it both before and after installing MacOSX Sierra, and I've noticed that some of the behavior is a bit strange. The code I use to detect a mouse press on a shape doesn't seem that reliable anymore. The handling of image compositing seems different. Maybe I've been coding against a buggy JVM and have been expecting certain behavior, but it's driving me nuts.