Convert List of one type to Array of another type using Java 8

Question

I need to convert List of string to Array of userdefinedType and for array I need to convert string to long.

I have achieved the same using below approach to achieve it

TeamsNumberIdentifier[] securityPolicyIdArray = securityPolicyIds.stream()
                .map(securityPolicy -> new TeamsNumberIdentifier(Long.valueOf(securityPolicy)))
                .collect(Collectors.toCollection(ArrayList::new))
                .toArray(new TeamsNumberIdentifier[securityPolicyIds.size()]);

Is there any better approach to convert this?

JB Nizet · Accepted Answer · 2016-12-14 18:35:30Z

7

You don't need to create a temporary ArrayList. Just use toArray() on the stream:

TeamsNumberIdentifier[] securityPolicyIdArray = securityPolicyIds.stream()
            .map(securityPolicy -> new TeamsNumberIdentifier(Long.valueOf(securityPolicy)))
            .toArray(TeamsNumberIdentifier[]::new);

But in general, I would tend to avoid arrays in the first place, and use lists instead.

answered Dec 14, 2016 at 18:35

JB Nizet

694k94 gold badges1.3k silver badges1.3k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

rajadilipkolli Over a year ago

I too does the same but my API needs arrays instead of lists

Nick Vanderhoven · Accepted Answer · 2016-12-15 05:51:52Z

1

I would write it like this:

securityPolicyIds.stream()
                 .map(Long::valueOf)
                 .map(TeamsNumberIdentifier::new)
                 .toArray(TeamsNumberIdentifier[]::new);

answered Dec 15, 2016 at 5:51

Nick Vanderhoven

3,09320 silver badges27 bronze badges

1 Comment

rajadilipkolli Over a year ago

This is more efficient one and more clean , I will use the same

Collectives™ on Stack Overflow

Convert List of one type to Array of another type using Java 8

2 Answers 2

1 Comment

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related