From http://java.net/jira/browse/MACOSX_PORT-153 --

Files.probeContentType return null for htm/html files

Test for reproducing issue:

import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class ContentTypeTest {

public static void main(String[] argv) {
String[] input = {"index.html", "index.htm"};
int failCount = 0;
try {
for (String s : input) {
Path path = Paths.get(s);
String filetype = Files.probeContentType(path);
if (filetype == null || !filetype.equals("text/html")) { System.out.println(path.toString() + " - file type is not text/html; file type is - " + filetype); failCount++; } else { System.out.println(path.toString() + " - file type is text/html"); }
}
} catch (Exception e) { e.printStackTrace(); }
if(failCount > 0) { System.out.println("TEST FAIL!"); } else { System.out.println("TEST PASS!"); }
}
}

Test result:

index.html - file type is not text/html; file type is - null
index.htm - file type is not text/html; file type is - null
TEST FAIL!