private static boolean lineExists(Optional<List<Map<String, Map<String, List<Map<String, String>>>>>> ordersOrNull, Line lineItem) { final String LINE_ITEMS = "lineItems"; final String ELEMENTS = "elements"; final String NOTE = "note"; MutableBoolean exists = new MutableBoolean(false); // if there is no order payload then the order hasn't already been posted so there can't be a duplicate line item ordersOrNull.ifPresent(orders -> { orders.stream().filter(order -> order.containsKey(LINE_ITEMS)) .map(order -> order.get(LINE_ITEMS)) .filter(lineItems -> lineItems.containsKey(ELEMENTS)) .flatMap(lineItems -> lineItems.get(ELEMENTS).stream()) .filter(element -> element.containsKey(NOTE) && element.get(NOTE).contains(lineItem.getNote())) .map(existingLine -> existingLine.get(NOTE)) .findAny() .ifPresent(n -> { System.out.println(String.format("Line item with note containing %s already exists in order.", lineItem.getNote())); exists.set(); }); }); return exists.get(); }