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.Product;
  43 import stream.data.Order;
  44 import java.util.List;
  45 import java.util.Map;
  46 import java.util.function.Function;
  47 import java.util.function.Predicate;
  48 import static java.util.stream.Collectors.*;
  49 
  50 /**
  51  * This class demos conditional filter usage for collection interface. Which
  52  * includes
  53  * 1. Simple filter on collection
  54  * 2. Combination of predicates filter on collection
  55  * 3. Grouping collection, also attach filter at the same time
  56  * @author tyan
  57  */
  58 public class Conditional extends DemoHelper {
  59     /**
  60      * Filter products that are out of stock. This is demo for simple filter for
  61      * one predicate. <p>
  62      *
  63      * @return     name list of product that is out of stock
  64      */
  65     public static List<String> outOfStock() {
  66         return products.stream().
  67                 //filter out of stock product
  68                 filter(p -> p.getUnitsInStock() == 0).
  69                 //map product to name
  70                 map(Product::getProductName).
  71                 //get product name list
  72                 collect(toList());
  73     }
  74 
  75     /*
  76      * Filter products that are in stock. This demo shows case that uses a given
  77      * predicate concatenate another predicate.
  78      *
  79      * @predicate  a predicate that filter on products
  80      * @return     product lists which fits predicate and in-sotck both
  81      */
  82     public static List<String> inStockWithPreicate(Predicate<Product> predicate) {
  83         //Oher way to do this is filter(isInStock).filter(predicate)
  84         return products.stream().
  85                 //filter product with predicate and in-stcok
  86                 filter(predicate.and(p -> p.getUnitsInStock() > 0))
  87                 //map product to name
  88                 .map(Product::getProductName).
  89                 //get product name lis
  90                 collect(toList());
  91     }
  92     /*
  93      * Filter customers in state and their orders, this is a demo for filter
  94      * predicate join with other data source
  95      *
  96      * @region     region be used to look for customer
  97      * @return     map from customer to its order list in given state
  98      */
  99 
 100     public static Map<Customer, List<Order>> customerMapOrdersFromRegion(
 101             String region) {
 102         return customers.stream()
 103                 //filter customer in given region
 104                 .filter(c -> region.equals(c.getRegion()))
 105                 //convert customers into a map, which key is customer, value is
 106                 //customer's list of orders
 107                 .collect(
 108                         //Accumulate customers into a Map, key is customer and value
 109                         //is cusromer's orders
 110                         toMap(Function.identity(), Customer::getOrders));
 111     }
 112 }