removeContribution(id);
removeContribution(Id);
	synchronized void addContribution(Contribution contribution) {		isDirty = true;		long id = contribution.getContributorId();		Long Id = new Long(id);		KeyedElement existingContribution = getFormerContributions().getByKey(Id);		if (existingContribution != null) { // move it from former to new contributions			removeContribution(id);			newContributions.add(existingContribution);		} else			existingContribution = newContributions.getByKey(Id);		if (existingContribution != null) // merge			((Contribution) existingContribution).mergeContribution(contribution);		else			newContributions.add(contribution);	}