ui/src/main/java/ucar/nc2/ui/widget/FileManager.java
public String chooseFilename() {
    if (!readOk) return null;
    selectedFile = false;
    //selectedURL = false;
    w.setVisible(true); // modal, so blocks; listener calls hide(), which unblocks.

    if (selectedFile) {
      File file = chooser.getSelectedFile();
      if (file == null) return null;
      try {
        return file.getCanonicalPath().replace('\\', '/');
      } catch (IOException ioe) {
      } // return null
    }

    /* if (selectedURL) {
      return (String) urlComboBox.getSelectedItem();
    }  */

    return null;
  }
public String chooseFilename() {
    if (!readOk) return null;
    selectedFile = false;
    //selectedURL = false;
    w.setVisible(true); // modal, so blocks; listener calls hide(), which unblocks.

    if (selectedFile) {
      File file = chooser.getSelectedFile();
      if (file == null) return null;
      try {
        return file.getCanonicalPath().replace('\\', '/');
      } catch (IOException ioe) {
      } // return null
    }

    /* if (selectedURL) {
      return (String) urlComboBox.getSelectedItem();
    }  */

    return null;
  }
Allow user to select file, then return the filename, in canonical form,
always using '/', never '\'

@return chosen filename in canonical form, or null if nothing chosen.