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Amazon Kinesis Streams
Developer Guide

Step 6: (Optional) Extending the Consumer

The application shown here may already be sufficient for your purposes. This optional section shows how you might want to extend the consumer code for a slightly more elaborate scenario.

If you want to know about the biggest sell orders each minute, this is a matter of modifying the StockStats class in three places to accommodate this new priority.

To extend the consumer

  1. Add new instance variables:

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    // 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. Add the following code to addStockTrade:

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    if (type == TradeType.SELL) { if (largestSellOrderStock == null || trade.getQuantity() > largestSellOrderQuantity) { largestSellOrderStock = trade.getTickerSymbol(); largestSellOrderQuantity = trade.getQuantity(); } }
  3. Modify the toString method to print the additional information:

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    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); }

If you run the consumer now (remember to run the producer also), you should see output similar to this:

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****** 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. ****************************************************************