exceptionally.java

private static void exception() {
   Integer age = -1;
   CompletableFuture<String> exceptionFuture = CompletableFuture.supplyAsync(() -> {
       if (age < 0) {
           throw new IllegalArgumentException("Age can not be negative");
       }
       if (age > 18) {
           return "Adult";
       } else {
           return "Child";
       }
   }).exceptionally(ex -> {
       System.out.println("Oops! We have an exception - " + ex.getMessage());
       return "Unknown!";
   });
   exceptionFuture.thenAccept(System.out::println); //Unknown!
}