I had added tiles.jar to the project libraries and when netbeans was still
running I replaced the file with a new one in windows explorer. In the source
window of a class which extends TilesServlet, I wanted to override a method. But
I couldnt the override option(i have created a seperate bug for that) so I
pressed ctrl+spacebar . I didnt see any of the parents method, jus the Object
class's methods. So to check if TileServlet had been included I placed the
cursor on the TilesServlet and pressed Ctrl+spacebar which is when the exception
was thrown.