Add examples of using max operator instead of sort and findFirst

aplotnikov · aplotnikov · commit 6839bcf8832b · 2018-12-26T19:49:07.000+01:00
diff --git a/src/main/java/io/github/aplotnikov/java_8_misuses/stream/collectors/TrueFunctionalApproach.java b/src/main/java/io/github/aplotnikov/java_8_misuses/stream/collectors/TrueFunctionalApproach.java
@@ -0,0 +1,59 @@
+package io.github.aplotnikov.java_8_misuses.stream.collectors;
+
+import io.github.aplotnikov.java_8_misuses.domain.Client;
+
+import java.util.List;
+
+import static io.github.aplotnikov.java_8_misuses.utils.Annotations.Good;
+import static io.github.aplotnikov.java_8_misuses.utils.Annotations.Ugly;
+import static java.util.Comparator.comparingInt;
+
+class TrueFunctionalApproach {
+    @Ugly
+    class BeforeJava8 {
+        Client findTheOldestClient(List<Client> clients) {
+            if (clients.isEmpty()) {
+                return null;
+            }
+
+            Client oldestClient = clients.iterator().next();
+            for (Client client : clients) {
+                if (client.getAge() > oldestClient.getAge()) {
+                    oldestClient = client;
+                }
+            }
+
+            return oldestClient;
+        }
+    }
+
+    @Ugly
+    class NaiveStreamsApproach {
+        Client findTheOldestClient(List<Client> clients) {
+            return clients.stream()
+                          .sorted(comparingInt(Client::getAge))
+                          .findFirst()
+                          .orElse(null);
+        }
+    }
+
+    @Ugly
+    class StreamsWithReduction {
+        Client findTheOldestClient(List<Client> clients) {
+            return clients.stream()
+                          .reduce((firstClient, secondClient) ->
+                                          firstClient.getAge() > secondClient.getAge() ? firstClient : secondClient
+                          )
+                          .orElse(null);
+        }
+    }
+
+    @Good
+    class MaxWithComparator {
+        Client findTheOldestClient(List<Client> clients) {
+            return clients.stream()
+                          .max(comparingInt(Client::getAge))
+                          .orElse(null);
+        }
+    }
+}
