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 }