Is there a way to compare two Strings with each other using java streams?

Question

This method compares two strings. One of them comes from an object. If the strings match, the id is returned by the object.


    private static Long getDefaultKag(Long mandandId) {
        List<MandantKagAccountEntity> mandantKagAccountEntities = new MandantKagAccountManager().findAllKags(mandandId);
        for (MandantKagAccountEntity mandantKagAccountEntity : mandantKagAccountEntities) {
            if (mandantKagAccountEntity.getKagText().equals("Default_kag")) {
                return mandantKagAccountEntity.getMandantKagId();
            }
        }
        return null;
    }

Is there any way to solve this with streams? My approach, but I can't get any further.

    private static long getDefaultKag(Long mandandId) {
        return new MandantKagAccountManager().findAllKags(mandandId).stream()
                .filter(m -> m.getKagText().equals("Default_Kag"))
                ...
                ...
                ...
    }

Do you have any idea how to solve this? I would also like to know which of the two variants is more efficient for large amounts of data.

score 5 · Accepted Answer · answered Aug 22 '19 at 11:49

5

Replace

...
...
...

with

.map(MandantKagAccountEntity::getMandantKagId)
.findFirst()
.orElse(null);

answered Aug 22 '19 at 11:49

Andrew Tobilko

48,120
14
91
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@Thilo you may want to return an `Optional`, or `OptionalLong` instead of `Long` – Andrew Tobilko Aug 22 '19 at 12:05
yeah maybe, i know that Optional, when filled, can not be zero anymore, right?. could you tell me the advantages if i would use Optional and how i can work with it afterwards? like normal? – Hubi Aug 22 '19 at 12:54
@Thilo here's a good topic https://stackoverflow.com/questions/23454952/uses-for-optional – Andrew Tobilko Aug 22 '19 at 12:56

yogev levi · Answer 2 · 2019-08-22T12:03:02.173

0

I think it will do the trick

      private static long getDefaultKag(Long mandandId) {
                MandantKagAccountManager mandantKagAccountManager=new MandantKagAccountManager().findAllKags(mandandId).stream()
                        .filter(m -> m.getKagText().equals("Default_Kag")).findFirst()
                        .orElse(null);
              if(mandantKagAccountManager!=null)
                    return mandantKagAccountManager.getMandantKagId()
               return null;
}

edited Aug 22 '19 at 12:03

answered Aug 22 '19 at 11:57

yogev levi

369
1
4
21

2

downvoted because of `MandantKagAccountManager.getMandantKagId()` and the general idea – Andrew Tobilko Aug 22 '19 at 12:02
2

you may map the optional to `MandantKagAccountEntity::getMandantKagId` and get rid of the if – Andrew Tobilko Aug 22 '19 at 12:03

Is there a way to compare two Strings with each other using java streams?

2 Answers2