Java SE specification states for java.awt.Component
  public Image createImage(int width,int height) method:
    "Returns:
        an off-screen drawable image, which can be used for double buffering.
        The return value may be null if the component is not displayable."

The "may" statement is not strong enough and means that non-null
return values are permitted. However, many Java implementations: 1.4.2,
5.0, 6.0, 7 behave to return "null" only. Moreover corresponding JCK
test requires "null".

In order to avoid confusion interpreting this specification assertion
and to prevent from JCK, TCK test challenges the spec wording must be
fixed to make "null" behavior concrete.