PathFileObject.toBinaryName() uses String.replace(String, String), which is profiling at 3x the cost of String.replace(char, char) on my machine. Switching to use the primitive version where possible saves ~300ms in a 30s compilation, or about 1%.

FileSystem.getSeperator() isn't guaranteed to return a single-character separator, but a simple check can satisfy all cases while still being optimal for single-character separators.