CreativeAssignment creativeAssignment = new CreativeAssignment();
creativeAssignment.setActive(true);
creativeAssignment.setCreativeId(creativeId);
// Create the click through URL.
ClickThroughUrl clickThroughUrl = new ClickThroughUrl();
clickThroughUrl.setDefaultLandingPageUsed(true);
clickThroughUrl.setLandingPageId(0);
creativeAssignment.setClickThroughUrl(clickThroughUrl);
// Create the creative assignments.
CreativeAssignment[] creativeAssignments = new CreativeAssignment[]{creativeAssignment};
rotationGroup.setCreativeAssignments(creativeAssignments);