Prove sulla concorrenza con ComposableFuture

modern-java/src/main/java/org/gym/fp/moderjava/ConcurrencyTest.java

@@ -1,9 +1,10 @@
 package org.gym.fp.moderjava;
 
-import java.util.concurrent.ExecutionException;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.Future;
+import org.gym.fp.moderjava.concurrent.Shop;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.concurrent.*;
 
 import static java.lang.System.out;
 
@@ -11,9 +12,10 @@ public class ConcurrencyTest {
 
     public static void main(String[] args) throws Exception {
         doExecutorsServiceTest();
+        doFutureTest();
     }
 
-    private static void doExecutorsServiceTest() throws ExecutionException, InterruptedException {
+    private static void doExecutorsServiceTest() throws Exception {
         int x = 1337;
         ExecutorService executorService = Executors.newFixedThreadPool(2);
         Future<Integer> y = executorService.submit(() -> f(x));
@@ -22,6 +24,18 @@ public class ConcurrencyTest {
         executorService.shutdown();
     }
 
+    private static void doFutureTest() throws Exception {
+        Collection<Shop> shops = getShops();
+        Future<Integer> future = CompletableFuture.supplyAsync(() -> {
+            out.println("Primo completable future");
+            return 10;
+        }).thenCombine(CompletableFuture.supplyAsync(() -> {
+            out.println("Secondo completable future");
+            return 30;
+        }), (first, second) -> first + second);
+        out.println(future.get(1, TimeUnit.NANOSECONDS));
+    }
+
     static int f(int x) {
         return 42;
     }
@@ -30,4 +44,17 @@ public class ConcurrencyTest {
         return x;
     }
 
+    static Collection<Shop> getShops() {
+        return Arrays.asList(
+                new Shop("BestShop1"),
+                new Shop("BestShop2"),
+                new Shop("BestShop3"),
+                new Shop("BestShop4"),
+                new Shop("BestShop5"),
+                new Shop("BestShop6"),
+                new Shop("BestShop7"),
+                new Shop("BestShop8")
+        );
+    }
+
 }

modern-java/src/main/java/org/gym/fp/moderjava/concurrent/Shop.java

@@ -0,0 +1,39 @@
+package org.gym.fp.moderjava.concurrent;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.ToString;
+
+import java.util.Random;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Future;
+
+@ToString
+@AllArgsConstructor
+public class Shop {
+
+    @Getter
+    private String name;
+
+    public double getPrice(String product) {
+        return calculatePrice(product);
+    }
+
+    public Future<Double> getPriceAsync(String product) {
+        return CompletableFuture.supplyAsync(() -> calculatePrice(product));
+    }
+
+    private double calculatePrice(String product) {
+        delay();
+        return new Random().nextDouble() * product.charAt(0) + product.charAt(1);
+    }
+
+    static void delay() {
+        try {
+            Thread.sleep(1000L);
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+}