Return values from Java Threads

Question

I have a Java Thread like the following:

   public class MyThread extends Thread {
        MyService service;
        String id;
        public MyThread(Stri         


        

Answer 1

In Java8 there is better way for doing this using CompletableFuture. Say we have class that get's id from the database, for simplicity we can just return a number as below,

static class GenerateNumber implements Supplier{

    private final int number;

    GenerateNumber(int number){
        this.number = number;
    }
    @Override
    public Integer get() {
        try {
            TimeUnit.SECONDS.sleep(1);
        }catch (InterruptedException e){
            e.printStackTrace();
        }
        return this.number;
    }
}

Now we can add the result to a concurrent collection once the results of every future is ready.

Collection results = new ConcurrentLinkedQueue<>();
int tasks = 10;
CompletableFuture[] allFutures = new CompletableFuture[tasks];
for (int i = 0; i < tasks; i++) {
     int temp = i;
     CompletableFuture future = CompletableFuture.supplyAsync(()-> new GenerateNumber(temp).get(), executor);
     allFutures[i] = future.thenAccept(results::add);
 }

Now we can add a callback when all the futures are ready,

CompletableFuture.allOf(allFutures).thenAccept(c->{
   System.out.println(results); // do something with result
});