A better way to compare Strings which could be null

Question

I was just wondering if there is a better way to do this. i feel it might be inefficient. Problem is for DB reasons i need to compare strings which can sometimes be null or not.

public static boolean compareStrings(String str1, String str2){

    if(str1 == null && str2 == null) return true;

    if(str1 != null && str2 != null){
        if(str1.equals(str2))
            return true;
    }

    return false;
}

migrate to http://codereview.stackexchange.com/...? – Abimaran Kugathasan Dec 01 '11 at 05:22 — Abimaran Kugathasan, Dec 01 '11 at 05:22
so sorry thanks will do so in future – Maurycy Dec 01 '11 at 05:24 — Maurycy, Dec 01 '11 at 05:24

score 49 · Accepted Answer · answered Dec 01 '11 at 05:21

49

The usual idiom is this:

return (str1 == null ? str2 == null : str1.equals(str2));

answered Dec 01 '11 at 05:21

Taymon

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22

I would like to just add that I was doing this for android and TextUtils.equals(a, b); does exactly this – Maurycy Dec 22 '11 at 01:14

score 34 · Answer 2 · edited Apr 26 '20 at 19:40

34

You say that these are potentially coming from a database. At that point, any inefficiencies around a few nullity tests are entirely insignificant compared with the cost of database queries, to be honest. I would focus on the readability.

To that end, I would start using Guava and its Objects class:

boolean equal = Objects.equal(a, b);

I would expect that to be implemented as per Taymon's code, basically - but it's nice to have it in one place.

EDIT: For Java 7+ you don't need Guava. You can just use java.util.Objects.equals(a, b).

edited Apr 26 '20 at 19:40

Unmitigated

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answered Dec 01 '11 at 05:27

Jon Skeet

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As far as "readability" ... that really makes me think of `object.ReferenceEquals`, which isn't a good thing :( – Dec 01 '11 at 05:46
@pst: It should make you think of the static `object.Equals` method, which is the equivalent already built-into .NET. – Jon Skeet Dec 01 '11 at 05:47
15

For anyone coming across this more recently, the same thing is now in Java 7: [Objects.equals](http://docs.oracle.com/javase/7/docs/api/java/util/Objects.html#equals%28java.lang.Object,%20java.lang.Object%29) – Steve Chambers Dec 12 '13 at 08:58

score 4 · Answer 3 · answered Dec 01 '11 at 05:28

4

If you are open to using apache Commons StringUtils then they have equals which compares two strings null-safe

answered Dec 01 '11 at 05:28

Bhavana C

69
1

score 1 · Answer 4 · answered Dec 01 '11 at 05:22

1

This code would only be inefficient if it causes a bottleneck during a normal execution of your program. The only way to know if this is the case is to run your program through a profiler. Until you do that and see for a fact that this function causes performance problems, I wouldn't worry about it.

answered Dec 01 '11 at 05:22

Dmitry B.

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It might be a bit picky for me to worry about this especially without profiling. I usually dont use profilers unless I come across memory leaks. I was more or less wondering if there was a better implementation than developing a static method of my own. Thank you – Maurycy Dec 01 '11 at 05:28

A better way to compare Strings which could be null

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