Filesystem case sensitive check and java.io.File#equals

[Jaikiran Pai]

In one of the projects that I'm involved in, we do a bunch of file
operations which sometimes need to check if a particular filesystem is
case sensitive. I was thinking of using java.io.File#equals since its
javadoc states:


/**
     * Tests this abstract pathname for equality with the given object.
     * Returns <code>true</code> if and only if the argument is not
     * <code>null</code> and is an abstract pathname that denotes the
same file
     * or directory as this abstract pathname.  Whether or not two abstract
     * pathnames are equal depends upon the underlying *system*.  On UNIX
     * systems, alphabetic case is significant in comparing pathnames;
on Microsoft Windows
     * systems it is not.
     *
     * @param   obj   The object to be compared with this abstract pathname
     *
     * @return  <code>true</code> if and only if the objects are the same;
     *          <code>false</code> otherwise
     */


My impression, based on that javadoc, was that the implementation of
that API will use the underlying _filesystem_ to decide whether or not
its case sensitive. However, my experiments on a macOS which is case
insensitive and also a basic check of the implementation code in the
JDK, shows that this uses a lexicographic check on the string
representation of the paths. Is that what this javadoc means by
"underlying system". I understand that there's a further sentence in
that javadoc which says UNIX systems are case significant and Windows
isn't. However, it wasn't fully clear to me that this API wouldn't
delegate it to the underlying filesystem on the OS.

While we are at it, is there a better API that can be used to do such a
case sensitivity check of the underlying filesystem? I checked the APIs
in java.nio.file but couldn't find anything relevant. If there isn't any
such API currently, is that something that can be introduced?

-Jaikiran