终止或破坏java 8流循环

我有一个java 8流循环，其中包含以下内容：

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 } }); } 

当满足某些条件时，如何摆脱循环？ 什么是关闭流的正确方法？

UPDATE

我误用了流tecnique，假设它是一个循环，它不是为此而设计的。 这是我最终使用的答案提供的代码：

  List 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，它不是为使用break这样的东西终止而设计的。 如果流是并行流，则lambda body可以同时在不同的线程上执行（不容易破坏，并且它可能很容易产生不正确的结果）。

更好地使用带有while循环的迭代器：

 Iterator 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; } } 

Answer 2

好吧，在流api中没有方法可以做到这一点（据我所知）。

但如果你真的需要它 ，你可以使用Exception。

编辑：对于给出这个答案-1的人，我不是在宣传这个应该遵循的方法，它只是你需要它的情况的一个选项，它确实回答了这个问题。

 public class BreakException extends RuntimeException {...} try { 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"); throw new BreakException() } }); } catch (BreakException e) { //Stoped }