（可選）擴展消費者 - Amazon Kinesis Data Streams
後續步驟

本文為英文版的機器翻譯版本，如內容有任何歧義或不一致之處，概以英文版為準。

（可選）擴展消費者

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

  1. 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;

  2. 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();
     }
 }

  3. 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.
  ****************************************************************

後續步驟

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