New evolution : adding comments/explanations

.gitignore

@@ -20,3 +20,8 @@
 
 # virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
 hs_err_pid*
+
+# other
+.idea
+target
+

src/main/java/com/example/completablefuture/CompletableFutureExamples2.java

@@ -0,0 +1,37 @@
+package com.example.completablefuture;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.function.Supplier;
+
+public class CompletableFutureExamples2 {
+    public static void main(String[] args) {
+
+        System.out.println("Beginning of the program");
+
+        CompletableFuture.supplyAsync(new Supplier<Integer>() {
+
+            @Override
+            public Integer get() {
+                return longNetworkProcess(5);
+            }
+        }).thenAccept(value -> System.out.println(value));
+
+        sleep(5);
+        System.out.println("End of the program");
+    }
+
+    public static int longNetworkProcess(int value) {
+        sleep(3);
+
+        return value * 10;
+    }
+
+    public static void sleep(int seconds) {
+        try {
+            Thread.sleep(seconds * 1000);
+        }
+        catch(InterruptedException e) {
+            e.printStackTrace();
+        }
+    }
+}

src/main/java/com/example/completablefuture/RealLifeCompletableFutureExample.java

@@ -12,6 +12,8 @@ public static void main(String[] args) {
         long start = System.currentTimeMillis();
 
         cars().thenCompose(cars -> {
+
+            // set the rating of each car
             List<CompletionStage<Car>> updatedCars = cars.stream()
                     .map(car -> rating(car.manufacturerId).thenApply(r -> {
                         car.setRating(r);
@@ -20,8 +22,10 @@ public static void main(String[] args) {
 
             CompletableFuture<Void> done = CompletableFuture
                     .allOf(updatedCars.toArray(new CompletableFuture[updatedCars.size()]));
+
             return done.thenApply(v -> updatedCars.stream().map(CompletionStage::toCompletableFuture)
                     .map(CompletableFuture::join).collect(Collectors.toList()));
+
         }).whenComplete((cars, th) -> {
             if (th == null) {
                 cars.forEach(System.out::println);
@@ -43,6 +47,7 @@ static CompletionStage<Float> rating(int manufacturer) {
                 Thread.currentThread().interrupt();
                 throw new RuntimeException(e);
             }
+
             switch (manufacturer) {
             case 2:
                 return 4f;
@@ -61,6 +66,7 @@ static CompletionStage<List<Car>> cars() {
         carList.add(new Car(1, 3, "Fiesta", 2017));
         carList.add(new Car(2, 7, "Camry", 2014));
         carList.add(new Car(3, 2, "M2", 2008));
+
         return CompletableFuture.supplyAsync(() -> carList);
     }