Java 8 Optional detect empty collection

Question

Using Java Optional:

List<String> myList = .... Optional.ofNullable(myList) .ifPresentOrElse(.. do something.., ()-> log.error("missing list"));

I do want to catch in logs when the list is null or empty. The above works perfectly for null. How can it be extended to catch the empty collections?

so you seriously think those streams are more readable than myList == null || myList.isEmpty()? — Andronicus
– Andronicus, Commented Apr 28, 2020 at 5:44

Hadi · Accepted Answer · 2020-04-28 07:04:13Z

4

if you really want to complicate things using Optional -

Optional.ofNullable(myList).filter(l -> !l.isEmpty()) .ifPresentOrElse(.. do something.., ()-> log.error("missing list"));

better would be using the if-else -

if(myList !=null && !myList.isEmpty()) { // do something } else { log.error("missing list"); }

further improvement - ensure that the List is not assigned a null value.

edited Apr 28, 2020 at 7:04

Hadi

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answered Apr 28, 2020 at 5:26

Naman

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4 Comments

janith1024 Over a year ago

if the myList is null 'filter(l -> !l.isEmpty())' will through null point exception

Naman Over a year ago

@janith1024 no it wouldn't, ofNullable would result in an empty Optional for such cases.

janith1024 Over a year ago

yes that true I have check the implementation of ofNullable. thanks for educate me

Holger Over a year ago

@janith1024 that’s the very purpose of Optional. It would render Optional completely useless if you still needed to perform null-checks in the chained operations.

Hadi · Accepted Answer · 2020-04-28 05:42:52Z

2

I think going with if()else{} is more readable. You can do like this:

Optional.ofNullable(myList == null || myList.isEmpty() ? null: myList) .ifPresentOrElse(.. do something.., ()-> log.error("missing list"));

edited Apr 28, 2020 at 5:42

answered Apr 28, 2020 at 5:38

Hadi

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3 Comments

Naman Over a year ago

I thought filter was a poor solution, its still better than this! :P

Hadi Over a year ago

@Naman filter does not cover OP requirement. OP wants to if mylist is empty log something.

Naman Over a year ago

thanks for the edit, and it does..if myList is empty it would result in an empty Optional and log something in the ifPresentorElse part.

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