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| 1 | +package org.codefx.demo.java10.lang.var; |
| 2 | + |
| 3 | +import java.util.List; |
| 4 | +import java.util.Map; |
| 5 | +import java.util.Map.Entry; |
| 6 | +import java.util.Optional; |
| 7 | +import java.util.stream.Stream; |
| 8 | + |
| 9 | +import static java.util.Map.entry; |
| 10 | + |
| 11 | +public class AdHocFields { |
| 12 | + |
| 13 | + /* |
| 14 | + * DOWNSIDES |
| 15 | + * |
| 16 | + * - verbose |
| 17 | + * - combination of non-trivial language features (anonymous types & type inference) |
| 18 | + * - falls apart when extracting methods |
| 19 | + * |
| 20 | + * ALTERNATIVES |
| 21 | + * |
| 22 | + * - Map.Entry |
| 23 | + * - a library offering tuples |
| 24 | + * - wait for records / data classes |
| 25 | + */ |
| 26 | + |
| 27 | + private static void process(User user, Map<User, SimpleAddress> addresses) { |
| 28 | + // with var it is possible to directly declare anonymous types |
| 29 | + // and refence their ad-hoc fields later |
| 30 | + var userWithAddress = new Object() { |
| 31 | + User _user = user; |
| 32 | + Optional<SimpleAddress> _address = Optional.ofNullable(addresses.get(user)); |
| 33 | + }; |
| 34 | + |
| 35 | + // further work with `userwithAddress` |
| 36 | + String asString = userWithAddress._user + " at " + userWithAddress._address; |
| 37 | + System.out.println(asString); |
| 38 | + } |
| 39 | + |
| 40 | + private static void processWithAnonymousType(List<User> users, Map<User, SimpleAddress> addresses) { |
| 41 | + // the stream pipeline works exactly the same in Java 8, but `userWithAddress` |
| 42 | + // would have to be `Optional<? extends Object>`, thus loosing the ad-hoc fields |
| 43 | + var userWithAddress = users.stream() |
| 44 | + .map(user -> new Object() { |
| 45 | + User _user = user; |
| 46 | + Optional<SimpleAddress> _address = Optional.ofNullable(addresses.get(user)); |
| 47 | + }) |
| 48 | + .filter(o -> o._address.isPresent()) |
| 49 | + .filter(o -> isValid(o._address.get())) |
| 50 | + .map(ua -> new Object() { |
| 51 | + User _user = ua._user; |
| 52 | + FullAddress _address = canonicalize(ua._address.get()); |
| 53 | + }) |
| 54 | + .findAny(); |
| 55 | + |
| 56 | + // further work with `userwithAddress` |
| 57 | + String asString = userWithAddress |
| 58 | + .map(ua -> ua._user + " at " + ua._address) |
| 59 | + .orElse("NONE"); |
| 60 | + System.out.println(asString); |
| 61 | + } |
| 62 | + |
| 63 | + private static void processWithEntries(List<User> users, Map<User, SimpleAddress> addresses) { |
| 64 | + // with `Entry` it is no longer necessary to rely on `var` - it is also shorter |
| 65 | + Optional<Entry<User, FullAddress>> userWithAddress = users.stream() |
| 66 | + .map(user -> entry(user, Optional.ofNullable(addresses.get(user)))) |
| 67 | + .filter(o -> o.getValue().isPresent()) |
| 68 | + .filter(o -> isValid(o.getValue().get())) |
| 69 | + .map(ua -> entry(ua.getKey(), canonicalize(ua.getValue().get()))) |
| 70 | + .findAny(); |
| 71 | + |
| 72 | + // further work with `userwithAddress` |
| 73 | + String asString = userWithAddress |
| 74 | + .map(ua -> ua.getKey() + " at " + ua.getValue()) |
| 75 | + .orElse("NONE"); |
| 76 | + System.out.println(asString); |
| 77 | + } |
| 78 | + |
| 79 | + private static boolean isValid(SimpleAddress address) { |
| 80 | + // fancy validation of `address` |
| 81 | + return true; |
| 82 | + } |
| 83 | + |
| 84 | + private static FullAddress canonicalize(SimpleAddress address) { |
| 85 | + // fancy processing of `address` |
| 86 | + return new FullAddress(address.address); |
| 87 | + } |
| 88 | + |
| 89 | + private static class User { |
| 90 | + |
| 91 | + private final String name; |
| 92 | + |
| 93 | + public User(String name) { |
| 94 | + this.name = name; |
| 95 | + } |
| 96 | + |
| 97 | + } |
| 98 | + |
| 99 | + private static class SimpleAddress { |
| 100 | + |
| 101 | + private final String address; |
| 102 | + |
| 103 | + public SimpleAddress(String address) { |
| 104 | + this.address = address; |
| 105 | + } |
| 106 | + } |
| 107 | + |
| 108 | + private static class FullAddress { |
| 109 | + |
| 110 | + private final String address; |
| 111 | + |
| 112 | + public FullAddress(String address) { |
| 113 | + this.address = address; |
| 114 | + } |
| 115 | + } |
| 116 | + |
| 117 | +} |
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