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There is a method get(sql) (I can not modify it). This method returns MyObjects and it has to be in try catch block because JqlParseException is possible there. My code is:

String sql = something; try{ MyObject object = get(sql); } catch(JqlParseException e){ e.printStackTrace(); } catch(RuntimeException e){ e.printStackTrace(); }

I want to remove try catch and use Optional class, I tried:

MyObject object = Optional.ofNullable(get(sql)).orElseThrow(RuntimeException::new);

but IDE force there try catch too. And for:

MyObject object = Optional.ofNullable(get(sql)).orElseThrow(JqlParseException::new));

is an error (in IDE) The type JqlParseException does not define JqlParseException() that is applicable. Is there any way to avoid try catch blocks and use optional?

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    Jump to the definition of get, see if it says throws JqlException. If it does, you must use try...catch. Commented Mar 24, 2017 at 7:13
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    It seems that quite a lot of people are considering Optional as the NextGeneration™ control flow construct. That's not going to happen. Optional, as well as its primitive counterparts, inherently can't handle this kind of task. It's not designed to completely replace control flow constructs like if-else or try-catch. Instead, it focuses on getting rid of those endless null checks. Commented Mar 24, 2017 at 7:31
  • @glee8e [Optional] focuses on getting rid of those endless null checks. I'd be more specific. Many people would jump to the conclusion that they ought to replace all occurrences of null with Optional, which goes against the intent of Optional's designers. Commented Mar 24, 2017 at 9:12
  • @Jubobs Maybe I'm still not senior enough to know where null can't be replaced with Optional, except in performance critical code or there is a design flaw. Please point out a situation, except those listed above, where null is used but Optional is not applicable. Commented Mar 25, 2017 at 11:47
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    @glee8e You shouldn't use Optional fields or parameters. As Brian Goetz puts it, [their] intention was to provide a limited mechanism for library method return types where there needed to be a clear way to represent "no result", and using null for such was overwhelmingly likely to cause errors. See also this great talk by Stuart Marks. Commented Mar 27, 2017 at 20:28

5 Answers 5

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Optional is not intended for the purpose of dealing with exceptions, it was intended to deal with potential nulls without breaking the flow of your program. For example:

 myOptional.map(Integer::parseInt).orElseThrow(() -> new RuntimeException("No data!");

This will automatically skip the map step if the optional was empty and go right to the throw step -- a nice unbroken program flow.

When you write:

 myOptionalValue.orElseThrow(() -> new RuntimeException("Unavailable"));

... what you are really saying is: Return my optional value, but throw an exception if it is not available.

What you seem to want is a way to create an optional (that instantly catches the exception) and will rethrow that exception when you try using the optional.

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3 Comments

how can we also attach the HttpStatus code with the exception in this example ?
@humbleCodes you can just throw a HttpStatusCodeException or ResponseStatusException, it will depend on the framework and what exceptions are available for this purpose. You can also define your own exception that accepts a status code.
do you know any resources which have used implementations for Spring/Spring Boot framework applications ?
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That's not how Optionals work. They don't make try-catch-blocks obsolete. However, you could introduce a new wrapper-function like this:

public Optional<MyObject> getMyObject(final String jql) { try { return Optional.ofNullable(get(sql)); } catch (final JqlParseException e) { return Optional.empty(); } }

You won't have to deal with the exception anymore, but you won't know if there was an error if you get an empty Optional as well.

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2

Try this

Optional.ofNullable(result) .orElseThrow(() -> new GenericClientException("Request body is not valid", HttpStatus.BAD_REQUEST));
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0

Optional helps to deal with NullPointerException.

You can use it to cast new exceptions as mentioned.

MyObject object = Optional.ofNullable(get(sql)).orElseThrow(RuntimeException::new);

However, your method get(sql) is not returning NULL, which invalidates the use of OPTIONAL as desired.

I would keep using Try Catch.

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if (StringUtils.isEmpty(message)) { throw new ValidationException("empty message body received from the queue");

in java 8

Optional.ofNullable(message).filter(message -> !message.isEmpty()).orElseThrow(() -> new ValidationException("empty message body received from the queue") );
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