The spec J2SE 5.0 has incorrect statements in JScrollPane javadoc:
 "public Component getCorner(String key)
  ..
  Returns: one of the components listed below or null if key is invalid:
           lowerLeft
           lowerRight
           upperLeft
           upperRight"

However, the current implementation returns null for valid keys. I assume the spec is incorrect
to not list this valid case. It should be explicitly stated that "or null if key is invalid or
if there is no corner component".

Also the spec mentions "By default, the corners are empty." which is hard to interpret.