@Override public Iterable<DefaultInvoice> prepareInvoices() throws InvoiceApiException { final DefaultInvoice invoice = getInvoiceAndCheckCurrency(invoiceId, currency, context); final InvoiceItem adjustmentItem = invoiceApiHelper.createAdjustmentItem(invoice, invoiceItemId, amount, currency, effectiveDate, description, itemDetails, internalCallContextFactory.createInternalCallContext(accountId, context)); if (adjustmentItem != null) { invoice.addInvoiceItem(adjustmentItem); } return ImmutableList.<DefaultInvoice>of(invoice); } };