Blogger - FPOWJPWB - Retry

/**
 * Generic method providing 'retry operation' capabilities.
 */
public final class Retry {
    private static final String DEFAULT_ERROR_MESSAGE = "Retries exhausted";

    public static <Result> Result retry(int times,
                                        Function0<Result> operation,
                                        Function1<Result, Boolean> checker,
                                        Function0<Void> preRetry,
                                        String errorMessage) throws Exception {
        Result operationResult = null;
        Exception operationException = null;
        try {
            operationResult = operation.apply();
        } catch (Exception e) {
            operationException = e;
        }

        final Result result;
        if (operationException == null && checker.apply(operationResult)) {
            result = operationResult;
        } else {
            if (times > 0) {
                if (preRetry != null) {
                    preRetry.apply();
                }
                result = retry(
                        times - 1, operation, checker, preRetry, errorMessage);
            } else {
                String message = errorMessage != null ? errorMessage : DEFAULT_ERROR_MESSAGE;
                throw operationException != null ? operationException : new Exception(message);
            }
        }

        return result;
    }

    private Retry() {
        // cannot instatiate
    }
}