Use Java 8 Optional features in the multiple null conditions

Use Java 8 Optional features in the multiple null conditions

The conditions is

Optional<Payee> payee = Optional.ofNullable(paymtTrans.getPayee());
    
    if (payee.isPresent()
            && payee.get().getPayeeAcc() != null
            && payee.get().getPayeeAcc().size() > 0
            && payee.get().getPayeeAcc().get(0).getBnk() != null
            && payee.get().getPayeeAcc().get(0).getBnk().getBnkCtryCode() != null) {
        String ctryCode = payee.get().getPayeeAcc().get(0).getBnk().getBnkCtryCode();
    }

The requirement is to use Java 8 features without checking the null values!!

Need to get the ctryCode??

Just use Optional.map(mapperFunction). If mapperFunction returns null, then .map returns an empty Optional:

Optional<Payee> payee = Optional.ofNullable(paymentTransaction.getPayee());
Optional<String> mayBeCountryCode = 
    payee
        .map(Payee::getPayeeAccounts)
        .filter(banks -> banks.size() > 0)
        .map(banks -> banks.get(0))
        .map(BankHolder::getBank)
        .map(Bank::getBankCountryCode);

UPD. You can do it more elegant with taking stream of banks:

Optional<Payee> payee = Optional.ofNullable(paymentTransaction.getPayee());
Optional<String> mayBeCountryCode = 
    payee
        .map(Payee::getPayeeAccounts)
        .map(Collection::stream)
        .flatMap(Stream::findFirst)
        .map(BankHolder::getBank)
        .map(Bank::getBankCountryCode);

Then you can use mayBeCountryCode, for example, like that:

    mayBeCountryCode.ifPresent(countryCode ->
            // do whatever with a non-null string
    );

    String countryCode = mayBeCountryCode.orElse("none");
    String nullableCountryCode = mayBeCountryCode.orElse(null);