I want to run 10 APIs in parallel. Each API returns some values. I want to stop when total count of values are equal to 100 i.e I don't want to wait for all the 10 APIs if I get my 100 results before getting results of all APIs.
So I was thinking to play with CompletableFuture.anyOf() in loop and return but I am unable to figure out the right syntax for the same. Also if there is some other efficient way to do so?
Please reply.
Thanks in advance!
You can use CountDownLatch
ExecutorService executor = Executors.newFixedThreadPool(10);
List<Integer> results = new ArrayList<>();
int maxResults = 100;
CountDownLatch latch = new CountDownLatch(maxResults);
for (int i = 0; i < 10; ++i) {
int apiNumber = i;
executor.execute(() -> {
while (results.size() < maxResults) {
try {
Thread.sleep(new Random().nextInt(1000));
System.out.println("API-" + apiNumber + " call");
int[] newValues = new Random().ints(0, 10).limit(new Random().nextInt(10)).toArray(); // API call
for (int value : newValues) {
synchronized (results) {
if (results.size() < maxResults) {
results.add(value);
latch.countDown();
}
}
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
}
latch.await();
System.out.println("The results have been calculated (" + results.size() + ")");
executor.shutdown();
or Phaser
ExecutorService executor = Executors.newFixedThreadPool(10);
List<Integer> results = new ArrayList<>();
int maxResults = 100;
Phaser phaser = new Phaser(1);
phaser.register();
for (int i = 0; i < 10; ++i) {
int apiNumber = i;
executor.execute(() -> {
while (results.size() < maxResults) {
try {
Thread.sleep(new Random().nextInt(1000));
System.out.println("API-" + apiNumber + " call");
int[] newValues = new Random().ints(0, 10).limit(new Random().nextInt(10)).toArray(); // API call
for (int value : newValues) {
synchronized (results) {
results.add(value);
if (results.size() >= maxResults) {
phaser.arrive();
break;
}
}
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
}
phaser.arriveAndAwaitAdvance();
System.out.println("The results have been calculated (" + results.size() + ")");
executor.shutdown();