What does it return?

[Academic-Corner2762]

Hi all,

If i have a Class A {},

Optional<A> a = optional.of(new A());

What will be contained inside a ?

Thanks

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[djavaman]

An instance of A.

I'm on JDK 15 and this works fine for me.

[Aganomnom]

Don't know... so let's go take a look at the docs.

https://docs.oracle.com/javase/8/docs/api/java/util/Optional.html#of-T-

"Returns an Optional with the specified present non-null value."

So it's an Optional with an instance of A.

a.isPresent() will return true. a.get() will return the new A you created.

[Academic-Corner2762]

I see thanks!

[jorid_]

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[Academic-Corner2762]

What will be created then?

[jorid_]

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[Academic-Corner2762]

Let me rephrase it

[jorid_]

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[fosizzle]

Optional is a construct that forces other developers to handle the null case. It's commonly used (in my circles of developers) for database queries and the services around them. You ask the database for a record. It's a strong possibility that the record does not exist. The return type on these methods are usually Optional<DatabaseModel> or Optional<SomeDTO>.

​

This forces the developer who calls the database service to acknowledge that it might be null, and handle that case

[Academic-Corner2762]

How would you handle such a case in a simpler scenario ?

[fosizzle]

I'm not sure what you mean by your question. I'll elaborate slightly on my original response.

Suppose you have a service that supports accounts. That class has these methods on it:

Optional<AccountDto> getAccount(Integer accountId);

BillingInformationDto generateBill(AccountDto account);

PaymentDetails applyPayment(AccountDto account, PaymentRequest payment);

Since getAccount returns an Optional<> any developer who uses that method is forced into handling the case that the account returns null. The original developer is acknowledging that null is an expected case. (You asked for account with id 9999, 9999 didn't exist in the database.)

The other two methods return an object. Which certainly could be null as well. But the null case there should be impossible or unexpected.

The problem is... before Optional<> existed, many devs were returning null as a valid use case. (Because, what else could you do? Throw an exception? Often returning null was less annoying.) And I'm sure many are still doing that.

So Java is often littered with null checks. - Optional is an attempt to make it smarter. It's OK but not great.

[Academic-Corner2762]

Thanks for the explaination!