How do I detect whether the file system is case-sensitive?

Don't use Strings to represent your files; use java.io.File:

http://java.sun.com/javase/6/docs/api/java/io/File.html#equals(java.lang.Object)

boolean isFileSystemCaseSensitive = !new File( "a" ).equals( new File( "A" ) );

It looks like you can use the IOCase.

Write a file named "HelloWorld"; attempt to read a file named "hELLOwORLD"?