Writing a method which can take another method and run that and if needed retry that execution given number of times. Using Runnable and scheduleAtFixedRate() from timer class.

TimerTask along with Timer class can schedule tasks using background thread. Timer has two type of scheduling option * schedule (Fixed delayed execution) * scheduleAtFixedRate (Fixed rate execution)

Fixed Delay Execution:

Execution after the first execution does not depend on the start time of the execution rather than the completion of the first execution then it starts the second execution

Fixed Rate Execution:

Execution after the first execution does depend on the start time of the execution. Second and execution afterwards

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	class Day26 {
    
        public static void main(String[] args) {
            retryMethod(() -> uptimeCheck("https://twitter.com"), 3, 5000L);                           
        }
    
        public static void retryMethod(Runnable function, int retryCount, long retryInterval) {
            Timer timer = new Timer();
            timer.scheduleAtFixedRate(new TimerTask() {
                int count = 0;
    
                @Override
                public void run() {
                    count++;
                    if (count == retryCount) {
                        timer.cancel();
                    }
                    try {
                        function.run();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }, 0, retryInterval);
        }
    
        public static void checkAvailability(String url) {
            HttpClient httpClient = HttpClient.newHttpClient();
            int statusCode = 0;
            HttpRequest httpRequest = HttpRequest
                    .newBuilder()
                    .uri(URI.create(url))
                    .GET()
                    .build();
            try {
                statusCode = httpClient.send(httpRequest, 		HttpResponse.BodyHandlers.ofString()).statusCode();
            } catch (IOException | InterruptedException e) {
                e.printStackTrace();
            }
    
            if (statusCode == 200)
                System.out.println(url + " is up and status: " + statusCode);
            else
                System.out.println(url + " is down and status: " + statusCode);
        }
    }

Here retryMethod is a method that takes a runnable and interval time and retry count to run the runnable using TimerTask and Timer’s scheduleAtFixedRate.

Furthermore here checkAvailability method takes an url and check if the url returns 200 thus getting a partial knowledge about if the site is up or down.