code: public Waiter<DescribeAppsRequest> appExists() {
  
          return new WaiterBuilder<DescribeAppsRequest, DescribeAppsResult>().withSdkFunction(new DescribeAppsFunction(client))
                  .withAcceptors(new HttpSuccessStatusAcceptor(WaiterState.SUCCESS), new HttpFailureStatusAcceptor(400, WaiterState.FAILURE))
                  .withDefaultPollingStrategy(new PollingStrategy(new MaxAttemptsRetryStrategy(40), new FixedDelayStrategy(1)))
                  .withExecutorService(executorService).build();
      }
docs: Builds a AppExists waiter by using custom parameters waiterParameters and other parameters defined in the waiters
  specification, and then polls until it determines whether the resource entered the desired state or not, where
  polling criteria is bound by either default polling strategy or custom polling strategy.