终止或中断java 8流循环[重复]

Question

我有一个包含以下内容的Java8流循环：

    void matchSellOrder(Market market, Order sellOrder) {
        System.out.println("selling " + market.pair() + " : " + sellOrder);

        market.buyOrders()
                .stream()
                .filter(buyOrder -> buyOrder.price >= sellOrder.price)
                .sorted(BY_ASCENDING_PRICE)
                .forEach((buyOrder) -> {
                    double tradeVolume = Math.min(buyOrder.quantity, sellOrder.quantity);
                    double price = buyOrder.price;

                    buyOrder.quantity -= tradeVolume;
                    sellOrder.quantity -= tradeVolume;

                    Trade trade = new Trade.Builder(market, price, tradeVolume, Trade.Type.SELL).build();
                    CommonUtil.convertToJSON(trade);

                    if (sellOrder.quantity == 0) {
                        System.out.println("order fulfilled");
                        // break loop there
                    }
                });
    }

        List<Order> applicableSortedBuyOrders = market.buyOrders()
                .stream()
                .filter(buyOrder -> buyOrder.price >= sellOrder.price)
                .sorted(BY_ASCENDING_PRICE)
                .collect(toList());

        for(Order buyOrder : applicableSortedBuyOrders){
            double tradeVolume = Math.min(buyOrder.quantity, sellOrder.quantity);
            double price = buyOrder.price;

            buyOrder.quantity -= tradeVolume;
            sellOrder.quantity -= tradeVolume;

            Trade trade = new Trade.Builder(market, price, tradeVolume, Trade.Type.SELL).build();
            CommonUtil.printAsJSON(trade);

            if (sellOrder.quantity == 0) {
                System.out.println("order fulfilled");
                break;
            }
        }

Answer 1

stream.foreach不是一个循环，也不是为了使用break之类的东西终止它而设计的。如果流是一个并行流，那么lambda主体可以同时在不同的线程上执行（不容易中断，而且很容易产生错误的结果）。

最好使用带有while循环的迭代器：

Iterator<BuyOrderType> iter = market.buyOrders() // replace BuyOrderType with correct type here
            .stream()
            .filter(buyOrder -> buyOrder.price >= sellOrder.price)
            .sorted(BY_ASCENDING_PRICE).iterator();
while (iter.hasNext()) {
    BuyOrderType buyOrder = iter.next()  // replace BuyOrderType with correct type here
    double tradeVolume = Math.min(buyOrder.quantity, sellOrder.quantity);
    double price = buyOrder.price;

    buyOrder.quantity -= tradeVolume;
    sellOrder.quantity -= tradeVolume;

    Trade trade = new Trade.Builder(market, price, tradeVolume, Trade.Type.SELL).build();
    CommonUtil.convertToJSON(trade);

    if (sellOrder.quantity == 0) {
        System.out.println("order fulfilled");
        break;
    }
}