There's room for a few minor cleanups in the UnixFileSystem/WinNTFileSystem implementation classes. In detail:

src/java.base/unix/classes/java/io/UnixFileSystem.java:
add missing @Override annotations

src/java.base/windows/classes/java/io/WinNTFileSystem.java:
remove an unnecessary local variable in public String resolve(File f)
add missing @Override annotations

src/java.base/unix/native/libjava/UnixFileSystem_md.c:
the fallback message for JNU_ThrowIOExceptionWithLastError in Java_java_io_UnixFileSystem_createFileExclusively should be aligned with the implementation in src/java.base/windows/native/libjava/WinNTFileSystem_md.c and should not yield the file path