Bug 315281 update copyrights for 3.6
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/internal/databinding/viewers/CheckboxViewerCheckedElementsProperty.java
private CheckStateListener(IProperty property,
				ISimplePropertyListener listener) {
			super(property, listener);
		}
		public void checkStateChanged(CheckStateChangedEvent event) {
			Object element = event.getElement();
			boolean checked = event.getChecked();
			Set elementSet = createElementSet((StructuredViewer) event
					.getCheckable());
			elementSet.add(element);
			Set additions = checked ? elementSet : Collections.EMPTY_SET;
			Set removals = checked ? Collections.EMPTY_SET : elementSet;
			SetDiff diff = Diffs.createSetDiff(additions, removals);
			fireChange(event.getSource(), diff);
		}
		public void doAddTo(Object source) {
			((ICheckable) source).addCheckStateListener(this);
		}
		public void doRemoveFrom(Object source) {
			((ICheckable) source).removeCheckStateListener(this);
		}
	}
	public String toString() {
		String s = "ICheckable.checkedElements{}"; 
		if (elementType != null)
			s += " <" + elementType + ">"; 
		return s;
	}
}