Java 8 method references: provide a Supplier capable of supplying a parameterized result

Question

I'd like to use

java.util.Optional.orElseThrow()

with an Exception type that asks for a constructor parameter. Something like this:

.orElseThrow(MyException::new(someArgument)) // obviously NOT working

Is there a way to create a Supplier that passes my argument value in?

Why can't you do `orElseThrow(() -> new MyException(someArgument))`? — Christoffer Hammarström, Apr 07 '14 at 15:51
Professional Java programmer with plenty of streams & Optional experience…I still end up here sometimes. And this is why I prefer Kotlin. — Drew Stephens, Jun 22 '18 at 19:54

score 603 · Accepted Answer · edited Jun 10 '20 at 13:43

603

Sure.

.orElseThrow(() -> new MyException(someArgument))

edited Jun 10 '20 at 13:43

simhumileco

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answered Apr 07 '14 at 15:50

Louis Wasserman

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Manu · Answer 2 · 2019-09-02T10:31:46.407

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It appears that you can throw only RuntimeException from the method orElseThrow. Otherwise you will get an error message like MyException cannot be converted to java.lang.RuntimeException

Update:- This was an issue with an older version of JDK. I don't see this issue with the latest versions.

edited Sep 02 '19 at 10:31

answered Feb 11 '15 at 09:03

Manu

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thanks, this was throwing me off when using `Optional` in groovy. Trying to `throw Exception` from a groovy closure, but it failed with `java.lang.reflect.UndeclaredThrowableException`, changing to a `RuntimeException` fixed it. – Ted Naleid Apr 12 '15 at 17:19
Good to know about that. Fortunately in my case, I'm using RuntimeExceptions, but this may not always be the case. – hbobenicio Jul 25 '17 at 15:15
**Incorrect** according to the class documentation for [`Optional.orElseThrow`](https://docs.oracle.com/javase/8/docs/api/java/util/Optional.html#orElseThrow-java.util.function.Supplier-) which says you can throw a [`Throwable`](https://docs.oracle.com/javase/8/docs/api/java/lang/Throwable.html) which means an `Error` or any `Exception`. – Basil Bourque Aug 23 '18 at 23:17
I think this was an issue with an older version of JDK 8. – Manu Dec 20 '18 at 07:35
@Manu Perhaps you are referring to [JDK-8047338](https://bugs.openjdk.java.net/browse/JDK-8047338) discussed on this Question, [*Throw RuntimeException inside Stream with Optional.orElseThrow*](https://stackoverflow.com/q/39076077/642706). If so, include in your Answer. I've not had quite enough coffee to discern if this is spot-on or not, so I'll refrain from editing your Answer myself. – Basil Bourque May 25 '19 at 17:08

score 13 · Answer 3 · edited Jun 27 '17 at 13:40

13

optionalUsers.orElseThrow(() -> new UsernameNotFoundException("Username not found"));

edited Jun 27 '17 at 13:40

Kartoch

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answered Jun 27 '17 at 13:17

Ashish Pushp

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i am getting error " The method orElseThrow(Supplier extends X>) in the type Optional is not applicable for the arguments (() -> {}) " – BdEngineer Jun 11 '19 at 07:16

Java 8 method references: provide a Supplier capable of supplying a parameterized result

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