title: Save FileDialog in Java strips initial file extension
body: <p>I'm using java.awt.FileDialog to create a dialog for saving a file. The problem is that when I specify a suggested (default) file name, FileDialog strips its extension. Example:</p>
  
  <pre><code>import java.awt.*;
  import java.io.*;
  
  public class SaveFile {
      public static void main(String[] args) {
          FileDialog fileDialog = new FileDialog(new Frame(), "Save", FileDialog.SAVE);
          fileDialog.setFilenameFilter(new FilenameFilter() {
              public boolean accept(File dir, String name) {
                  return name.endsWith(".txt");
              }
          });
          fileDialog.setFile("Untitled.txt");
          fileDialog.setVisible(true);
          System.out.println("File: " + fileDialog.getFile());
      }
  }
  </code></pre>
  
  <p>I would expect that when the FileDialog appears, the default file name is "Untitled.txt", but instead it is just "Untitled". When users click Save, I get back a filename without the extension. FileDialog does this on both Windows and OS X.</p>
  
  <p>I don't get it. Why would FileDialog deliberately strip the extension? Is there some logical reason for this? The documentation doesn't discuss it. As a workaround, I could simply add the extension to the string that FileDialog returns, but still, this seems like a bug...</p>
  
  <p>(Note that I cannot use JFileChooser; I need the native AWT FileDialog.)</p>