（選用）擴展消費者

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（選用）擴展消費者 - Amazon Kinesis Data Streams

後續步驟

教學課程：使用 KPL 和 KCL 1.x 處理即時庫存資料所述的應用程式可能已足以達到您的目的。此一選用章節示範如何就更為複雜的情境擴充消費者程式碼。

如果您想知道每分鐘銷售量最高的訂單，則可修改三處位置的 StockStats 類別以納入這項新的優先等級。

擴充消費者

加入新的執行個體變數：


 // Ticker symbol of the stock that had the largest quantity of shares sold 
 private String largestSellOrderStock;
 // Quantity of shares for the largest sell order trade
 private long largestSellOrderQuantity;

為 addStockTrade 添加以下程式碼：


 if (type == TradeType.SELL) {
     if (largestSellOrderStock == null || trade.getQuantity() > largestSellOrderQuantity) {
         largestSellOrderStock = trade.getTickerSymbol();
         largestSellOrderQuantity = trade.getQuantity();
     }
 }

修改 toString 方法以列印其他資訊：


 public String toString() {
     return String.format(
             "Most popular stock being bought: %s, %d buys.%n" +
             "Most popular stock being sold: %s, %d sells.%n" +
             "Largest sell order: %d shares of %s.",
             getMostPopularStock(TradeType.BUY), getMostPopularStockCount(TradeType.BUY),
             getMostPopularStock(TradeType.SELL), getMostPopularStockCount(TradeType.SELL),
             largestSellOrderQuantity, largestSellOrderStock);
 }

若您現在執行消費者 (記得也要執行生產者)，應會看到類似以下內容的輸出：


 ****** Shard shardId-000000000001 stats for last 1 minute ******
  Most popular stock being bought: WMT, 27 buys.
  Most popular stock being sold: PTR, 14 sells.
  Largest sell order: 996 shares of BUD.
  ****************************************************************