[java] Why can't I overload my methods?

public class FileStructure
{
  public void addDirectory(File root, boolean subfolders) throws
      InvalidDirectoryException
  {
    //...
  }


  public void removeDirectory(File root)
  {
    //...
  }


  public boolean updateFileStructure()
  {
    //...
  }


  public Vector describe()
  {
    //...
  }

  public DefaultMutableTreeNode describe()
  {
    //...
  }

  private class InvalidDirectoryException extends Exception
  {
    public InvalidDirectoryException()
    {

    }
  }
}