showOpenDialog different in Mac and Win

Question

I am writing a simple filechooser and in it I have the code:

JFileChooser fc = new JFileChooser();
int result = fc.showOpenDialog(null);  

When I run this under Windows (7) I get a chooser with a text field in which I can enter a file name (Note the File: [text box] at the bottom):

But when I run the same code on a Mac (OSX Mavericks) I get a window with no option to enter a filename:

I found that I can get around this by using fc.showDialog instead, (or probably showSaveDialog with customized text, though I haven't tried that) but I'm wondering why there would be this difference in the platforms. I work at home under Windows then teach a class on a Mac. It's embarrassing to have my example code not work correctly!

TIA for any insights or advice.