Returns the application defined property of the receiver
with the specified name, or null if it has not been set.
<p>
Applications may have associated arbitrary objects with the
receiver in this fashion. If the objects stored in the
properties need to be notified when the widget is disposed
of, it is the application's responsibility to hook the
Dispose event on the widget and do so.
</p>
@param key the name of the property
@return the value of the property or null if it has not been set
@exception SWTException <ul>
<li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
<li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
</ul>
Returns the application defined property of the receiver with the specified name, or null if it has not been set. <p> Applications may have associated arbitrary objects with the receiver in this fashion. If the objects stored in the properties need to be notified when the widget is disposed of, it is the application's responsibility to hook the Dispose event on the widget and do so. </p>
@param key the name of the property @return the value of the property or null if it has not been set
@exception SWTException <ul> <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li> <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li> </ul>
@see #setData(String, Object)