private final static void updateGuessTable(String mimetype,String ext)
 {
 	 if(mimetype==null || ext==null) return;
	 if(mimetype.length()==0 || ext.length()==0) return;
	 ext=("."+ext).toLowerCase();
	 for(int i=0;i<guesstable.length;i+=2)
	 {
		 if(ext.equals(guesstable[i]))
		   {
		     guesstable[i+1]=mimetype;
		     return;
		   }
	 }
	 String tmp[];
	 tmp=new String[guesstable.length+2];
	 System.arraycopy(guesstable,0,tmp,0,guesstable.length);
	 tmp[guesstable.length]=ext;
	 tmp[guesstable.length+1]=mimetype;
	 guesstable=tmp;
}