allOf.java

private static void allOf() {
   CompletableFuture<String> completableFuture1
           = CompletableFuture.supplyAsync(() -> "Hello");
   CompletableFuture<String> completableFuture2
           = CompletableFuture.supplyAsync(() -> "Knolders!");
   CompletableFuture<String> completableFuture3
           = CompletableFuture.supplyAsync(() -> "Its allOf");

   CompletableFuture<Void> combinedFuture
           = CompletableFuture.allOf(completableFuture1, completableFuture2, completableFuture3);
}