Stream with Try example.

demo/03/src/main/java/pl/amu/edu/demo/stream/StreamExample.java

@@ -0,0 +1,65 @@
+package pl.amu.edu.demo.stream;
+
+import io.vavr.control.Try;
+import pl.amu.edu.demo.data.Address;
+import pl.amu.edu.demo.data.Housing;
+import pl.amu.edu.demo.data.Person;
+
+import java.time.LocalDate;
+import java.util.OptionalDouble;
+import java.util.concurrent.ForkJoinPool;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.Stream;
+
+public class StreamExample {
+
+    public static void main(String[] args) {
+        new StreamExample().run();
+    }
+
+    private void run() {
+        // Huge number of threads!
+        getPeople().parallel().mapToInt(Person::getAge).average().ifPresent(System.out::println);
+        // Better solution, limiting the number of threads
+        try (var pool = new ForkJoinPool(8)) {
+            var maybeAverageAgeFuture = pool.submit(
+                    () -> getPeople().parallel().mapToInt(Person::getAge).average()
+            );
+            // io.vavr.control.Try
+            var triedAverageAge = Try.of(
+                    () -> maybeAverageAgeFuture.get(30, TimeUnit.SECONDS)
+            ).map(OptionalDouble::orElseThrow);
+            if (triedAverageAge.isSuccess()) { // there is also isFailure()
+                System.out.println(triedAverageAge.get()); // instead of if, one can use getOrElse()
+            }
+        }
+
+    }
+
+    private Stream<Person> getPeople() {
+        var personPrototype = Person.builder()
+                .housing(
+                        Housing.builder().isApartment(false).area(54321.0).address(
+                                Address.builder().build()
+                        ).build()
+                );
+        return Stream.of(
+                personPrototype
+                        .displayName("Maksymilian Paradys")
+                        .birthDate(LocalDate.of(1958, 10, 25))
+                        .build(),
+                personPrototype
+                        .displayName("Albert Starski")
+                        .birthDate(LocalDate.of(1958, 4, 6))
+                        .build(),
+                personPrototype
+                        .displayName("Lamia Reno")
+                        .birthDate(LocalDate.of(2017, 3, 11))
+                        .build(),
+                personPrototype.displayName("Emma Dax")
+                        .birthDate(LocalDate.of(2014, 11, 17))
+                        .build()
+        );
+    }
+
+}