1 /*
   2  * Copyright (c) 2013 Oracle and/or its affiliates. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  *
   8  *   - Redistributions of source code must retain the above copyright
   9  *     notice, this list of conditions and the following disclaimer.
  10  *
  11  *   - Redistributions in binary form must reproduce the above copyright
  12  *     notice, this list of conditions and the following disclaimer in the
  13  *     documentation and/or other materials provided with the distribution.
  14  *
  15  *   - Neither the name of Oracle nor the names of its
  16  *     contributors may be used to endorse or promote products derived
  17  *     from this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  20  * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  24  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  25  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  26  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  27  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  28  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  29  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  30  */
  31 
  32 /*
  33  * This source code is provided to illustrate the usage of a given feature
  34  * or technique and has been deliberately simplified. Additional steps
  35  * required for a production-quality application, such as security checks,
  36  * input validation and proper error handling, might not be present in
  37  * this sample code.
  38  */
  39 package stream;
  40 
  41 import stream.data.Customer;
  42 import stream.data.Order;
  43 import java.util.Map;
  44 import java.util.function.Function;
  45 import static java.util.stream.Collectors.toConcurrentMap;
  46 
  47 public class Selection extends DemoHelper {
  48 
  49     /**
  50      * Mapping customer to its total order price, only customer whose total
  51      * order price is bigger than bigValue will be put into the map
  52      *
  53      * @param bigValue customer's total price low limit
  54      * @return a map which map customer to its order price
  55      */
  56     public static Map<Customer, Double> bigOrderCustomers(double bigValue) {
  57         Function<Customer, Double> orderTotal
  58                 = c -> c.getOrders().stream().
  59                 //map order to order price
  60                 mapToDouble(Order::getTotal).
  61                 //calculate total price
  62                 sum();
  63         Map<Customer, Double> customersToBigOrder = customers.stream().
  64                 //grouping customer to a Map which key is customer, value is
  65                 //total order price
  66                 collect(toConcurrentMap(Function.identity(),
  67                                 orderTotal));
  68         customersToBigOrder.forEach((customer, totalAmount) -> {
  69             //Remove all customer whose total order amount is not greater than
  70             //bigValue
  71             if (totalAmount <= bigValue) {
  72                 customersToBigOrder.remove(customer);
  73             }
  74         });
  75         return customersToBigOrder;
  76     }
  77 }