FlatMapOptional.java

public static void main(String[] args) {
    Optional<String> mapped = getMerchantOrderIdFromUrl("haveId").map(orderId -> {
        return orderId + " mapped";
    });
 
    System.out.println(mapped);
 
    Optional<Optional<String>> merchant = getMerchantOrderIdFromUrl("haveId").map(orderId -> {
        return getMerchant(orderId);
    });
 
    Optional<String> merchantf = getMerchantOrderIdFromUrl("haveId").flatMap(orderId -> {
        return getMerchant(orderId);
    });
}
 
 
static Optional<String> getMerchantOrderIdFromUrl(String requestUri) {
    if(requestUri.equals("haveId")) {
        return Optional.of("1");
    }
    return Optional.empty();
}
 
static Optional<String> getMerchant(String id) {
    if (id.equals("1")) {
        return Optional.of("Merchant");
    }
    return Optional.empty();
}