Multiple null checks in Java 8
63
I have the below code which is bit ugly for multiple null checks.
String s = null;
if (str1 != null) {
s = str1;
} else if (str2 != null) {
s = str2;
} else if (str3 != null) {
s = str3;
} else {
s = str4;
}
So I tried using Optional.ofNullable like below, but its still difficult to understand if someone reads my code. what is the best approach to do that in Java 8.
String s = Optional.ofNullable(str1)
.orElse(Optional.ofNullable(str2)
.orElse(Optional.ofNullable(str3)
.orElse(str4)));
In Java 9, we can use Optional.ofNullablewith OR, But in Java8 is there any other approach ?
java java-8
edited Feb 21 at 15:22
Olivier Grégoire
15.3k1663104
asked Feb 21 at 6:45
sparkersparker
651816
|
show 4 more comments
63
I have the below code which is bit ugly for multiple null checks.
String s = null;
if (str1 != null) {
s = str1;
} else if (str2 != null) {
s = str2;
} else if (str3 != null) {
s = str3;
} else {
s = str4;
}
So I tried using Optional.ofNullable like below, but its still difficult to understand if someone reads my code. what is the best approach to do that in Java 8.
String s = Optional.ofNullable(str1)
.orElse(Optional.ofNullable(str2)
.orElse(Optional.ofNullable(str3)
.orElse(str4)));
In Java 9, we can use Optional.ofNullablewith OR, But in Java8 is there any other approach ?
java java-8
edited Feb 21 at 15:22
Olivier Grégoire
15.3k1663104
asked Feb 21 at 6:45
sparkersparker
651816
3
Java9orsyntaxString s = Optional.ofNullable(str1) .or(() -> Optional.ofNullable(str2)) .or(() -> Optional.ofNullable(str3)) .orElse(str4);looks not as good as theStream.ofI would sya.
– nullpointer
Feb 21 at 6:55
1
@OleV.V. Nothing wrong, the OP is already aware of it and is seeking something specific to Java-8.
– nullpointer
Feb 21 at 8:12
2
I know the user is asking for Java-8 specific solution, but on a general note, I would go withStringUtils.firstNonBlank()
– Mohamed Anees A
Feb 21 at 12:09
2
Problem is, Java 8/streams isn't the best solution for this. That code really smells like a refactor is in order but without more context it's really hard to tell. For starters--why aren't three objects that are probably so closely related not already in a collection?
– Bill K
Feb 21 at 17:49
1
@MohamedAneesA would have provided the best answer (as a comment) but didn't specify the source of StringUtils in this case. At any rate, if you HAVE to have these as a bunch of separate strings, coding it as a vargs method like "firstNonBlank" is ideal, the syntax inside will be an array making a simple for-each loop with a return on finding a non-null value trivial and obvious. In this case, java 8 streams are an attractive nuisance. they tempt you to inline and complicate something that should be a simple method/loop.
– Bill K
Feb 21 at 17:55
|
show 4 more comments
63
63
63
12
I have the below code which is bit ugly for multiple null checks.
String s = null;
if (str1 != null) {
s = str1;
} else if (str2 != null) {
s = str2;
} else if (str3 != null) {
s = str3;
} else {
s = str4;
}
So I tried using Optional.ofNullable like below, but its still difficult to understand if someone reads my code. what is the best approach to do that in Java 8.
String s = Optional.ofNullable(str1)
.orElse(Optional.ofNullable(str2)
.orElse(Optional.ofNullable(str3)
.orElse(str4)));
In Java 9, we can use Optional.ofNullablewith OR, But in Java8 is there any other approach ?
java java-8
edited Feb 21 at 15:22
Olivier Grégoire
15.3k1663104
asked Feb 21 at 6:45
sparkersparker
651816
I have the below code which is bit ugly for multiple null checks.
String s = null;
if (str1 != null) {
s = str1;
} else if (str2 != null) {
s = str2;
} else if (str3 != null) {
s = str3;
} else {
s = str4;
}
So I tried using Optional.ofNullable like below, but its still difficult to understand if someone reads my code. what is the best approach to do that in Java 8.
String s = Optional.ofNullable(str1)
.orElse(Optional.ofNullable(str2)
.orElse(Optional.ofNullable(str3)
.orElse(str4)));
In Java 9, we can use Optional.ofNullablewith OR, But in Java8 is there any other approach ?
java java-8
java java-8
edited Feb 21 at 15:22
Olivier Grégoire
15.3k1663104
asked Feb 21 at 6:45
sparkersparker
651816
edited Feb 21 at 15:22
Olivier Grégoire
15.3k1663104
asked Feb 21 at 6:45
sparkersparker
651816
edited Feb 21 at 15:22
Olivier Grégoire
15.3k1663104
edited Feb 21 at 15:22
Olivier Grégoire
15.3k1663104
edited Feb 21 at 15:22
Olivier Grégoire
15.3k1663104
15.3k1663104
asked Feb 21 at 6:45
sparkersparker
651816
asked Feb 21 at 6:45
sparkersparker
651816
asked Feb 21 at 6:45
sparkersparker
651816
651816
3
Java9orsyntaxString s = Optional.ofNullable(str1) .or(() -> Optional.ofNullable(str2)) .or(() -> Optional.ofNullable(str3)) .orElse(str4);looks not as good as theStream.ofI would sya.
– nullpointer
Feb 21 at 6:55
1
@OleV.V. Nothing wrong, the OP is already aware of it and is seeking something specific to Java-8.
– nullpointer
Feb 21 at 8:12
2
I know the user is asking for Java-8 specific solution, but on a general note, I would go withStringUtils.firstNonBlank()
– Mohamed Anees A
Feb 21 at 12:09
2
Problem is, Java 8/streams isn't the best solution for this. That code really smells like a refactor is in order but without more context it's really hard to tell. For starters--why aren't three objects that are probably so closely related not already in a collection?
– Bill K
Feb 21 at 17:49
1
@MohamedAneesA would have provided the best answer (as a comment) but didn't specify the source of StringUtils in this case. At any rate, if you HAVE to have these as a bunch of separate strings, coding it as a vargs method like "firstNonBlank" is ideal, the syntax inside will be an array making a simple for-each loop with a return on finding a non-null value trivial and obvious. In this case, java 8 streams are an attractive nuisance. they tempt you to inline and complicate something that should be a simple method/loop.
– Bill K
Feb 21 at 17:55
|
show 4 more comments
3
Java9orsyntaxString s = Optional.ofNullable(str1) .or(() -> Optional.ofNullable(str2)) .or(() -> Optional.ofNullable(str3)) .orElse(str4);looks not as good as theStream.ofI would sya.
– nullpointer
Feb 21 at 6:55
1
@OleV.V. Nothing wrong, the OP is already aware of it and is seeking something specific to Java-8.
– nullpointer
Feb 21 at 8:12
2
I know the user is asking for Java-8 specific solution, but on a general note, I would go withStringUtils.firstNonBlank()
– Mohamed Anees A
Feb 21 at 12:09
2
Problem is, Java 8/streams isn't the best solution for this. That code really smells like a refactor is in order but without more context it's really hard to tell. For starters--why aren't three objects that are probably so closely related not already in a collection?
– Bill K
Feb 21 at 17:49
1
@MohamedAneesA would have provided the best answer (as a comment) but didn't specify the source of StringUtils in this case. At any rate, if you HAVE to have these as a bunch of separate strings, coding it as a vargs method like "firstNonBlank" is ideal, the syntax inside will be an array making a simple for-each loop with a return on finding a non-null value trivial and obvious. In this case, java 8 streams are an attractive nuisance. they tempt you to inline and complicate something that should be a simple method/loop.
– Bill K
Feb 21 at 17:55
3
3
Java9
or syntax String s = Optional.ofNullable(str1) .or(() -> Optional.ofNullable(str2)) .or(() -> Optional.ofNullable(str3)) .orElse(str4); looks not as good as the Stream.of I would sya.– nullpointer
Feb 21 at 6:55
Java9
or syntax String s = Optional.ofNullable(str1) .or(() -> Optional.ofNullable(str2)) .or(() -> Optional.ofNullable(str3)) .orElse(str4); looks not as good as the Stream.of I would sya.– nullpointer
Feb 21 at 6:55
1
1
@OleV.V. Nothing wrong, the OP is already aware of it and is seeking something specific to Java-8.
– nullpointer
Feb 21 at 8:12
@OleV.V. Nothing wrong, the OP is already aware of it and is seeking something specific to Java-8.
– nullpointer
Feb 21 at 8:12
2
2
I know the user is asking for Java-8 specific solution, but on a general note, I would go with
StringUtils.firstNonBlank()– Mohamed Anees A
Feb 21 at 12:09
I know the user is asking for Java-8 specific solution, but on a general note, I would go with
StringUtils.firstNonBlank()– Mohamed Anees A
Feb 21 at 12:09
2
2
Problem is, Java 8/streams isn't the best solution for this. That code really smells like a refactor is in order but without more context it's really hard to tell. For starters--why aren't three objects that are probably so closely related not already in a collection?
– Bill K
Feb 21 at 17:49
Problem is, Java 8/streams isn't the best solution for this. That code really smells like a refactor is in order but without more context it's really hard to tell. For starters--why aren't three objects that are probably so closely related not already in a collection?
– Bill K
Feb 21 at 17:49
1
1
@MohamedAneesA would have provided the best answer (as a comment) but didn't specify the source of StringUtils in this case. At any rate, if you HAVE to have these as a bunch of separate strings, coding it as a vargs method like "firstNonBlank" is ideal, the syntax inside will be an array making a simple for-each loop with a return on finding a non-null value trivial and obvious. In this case, java 8 streams are an attractive nuisance. they tempt you to inline and complicate something that should be a simple method/loop.
– Bill K
Feb 21 at 17:55
@MohamedAneesA would have provided the best answer (as a comment) but didn't specify the source of StringUtils in this case. At any rate, if you HAVE to have these as a bunch of separate strings, coding it as a vargs method like "firstNonBlank" is ideal, the syntax inside will be an array making a simple for-each loop with a return on finding a non-null value trivial and obvious. In this case, java 8 streams are an attractive nuisance. they tempt you to inline and complicate something that should be a simple method/loop.
– Bill K
Feb 21 at 17:55
|
show 4 more comments
7 Answers
7
active
oldest
votes
125
You may do it like so:
String s = Stream.of(str1, str2, str3)
.filter(Objects::nonNull)
.findFirst()
.orElse(str4);
edited Feb 22 at 8:57
Sulthan
97.4k16158202
answered Feb 21 at 6:51
Ravindra RanwalaRavindra Ranwala
10.6k42040
13
This. Think in what you need, not what you have.
– Thorbjørn Ravn Andersen
Feb 21 at 8:23
17
How much is the speed overhead? Creating Stream objects, calling 4 methods, creating temporary arrays ({str1, str2, str3}) look like much slower than a localifor?:, which the Java runtime can optimize. Is there some Stream-specific optimization injavacand the Java runtime which makes it as fast as?:? If not, I won't recommend this solution in performance-critical code.
– pts
Feb 21 at 9:58
13
@pts this is very likely to be slower than?:code and I'm sure you should avoid it in performance-critical code. It's however much more readable and you should recommend it in non-performance-critical code IMO, which I'm sure makes more than 99% of code.
– Aaron
Feb 21 at 10:39
34
Insert mandatory premature optimization comment.
– Sebastiaan van den Broek
Feb 21 at 12:31
17
Great solution! To increase readability a little bit I would suggest to addstr4to the parameters ofStream.of(...)and useorElse(null)in the end.
– danielp
Feb 21 at 23:12
|
show 4 more comments
64
How about ternary conditional operator?
String s =
str1 != null ? str1 :
str2 != null ? str2 :
str3 != null ? str3 : str4
;
edited Feb 21 at 19:42
candied_orange
4,3221648
answered Feb 21 at 6:48
EranEran
287k37467556
47
actually, he's looking for "the best approach to do this in Java8". This approach can be used in Java8, so it all just depends on what the OP means by "the best", and on which grounds he bases the decision of what is better on.
– Stultuske
Feb 21 at 7:13
17
I usually dislike nested ternaries, but this looks pretty clean.
– JollyJoker
Feb 21 at 8:59
9
This is a huge pain to parse for anyone who isn't reading nested ternary operators every day.
– Cubic
Feb 21 at 15:46
1
@Cubic: If you think it's hard to parse, write a comment like// take first non-null of str1..3. Once you know what it does, it becomes easy to see how.
– Peter Cordes
Feb 22 at 3:36
4
@Cubic Yet, this is a simple repeated pattern. Once you parsed line 2, you've parsed the entire thing, no matter how many cases are included. And once you are done, you've learned to express a similar selection of ten different cases in a brief, and relatively simple manner. The next time you'll see a?:ladder, you'll know what it does. (Btw, functional programmers know this as(cond ...)clauses: It's always a guard followed by the appropriate value to use when the guard is true.)
– cmaster
Feb 22 at 17:18
|
show 1 more comment
28
You can also use a loop:
String strings = {str1, str2, str3, str4};
for(String str : strings) {
s = str;
if(s != null) break;
}
answered Feb 21 at 6:52
ernest_kernest_k
23.1k42647
add a comment |
20
Current answers are nice but you really should put that in a utility method:
public static Optional<String> firstNonNull(String... strings) {
return Arrays.stream(strings)
.filter(Objects::nonNull)
.findFirst();
}
That method has been in my Util class for years, makes code much cleaner:
String s = firstNonNull(str1, str2, str3).orElse(str4);
You can even make it generic:
public static <T> Optional<T> firstNonNull(T... objects) {
return Arrays.stream(objects)
.filter(Objects::nonNull)
.findFirst();
}
// Use
Student student = firstNonNull(student1, student2, student3).orElseGet(Student::new);
answered Feb 21 at 8:51
walenwalen
3,87211539
8
FWIW, in SQL, this function is called coalesce, so i call it that in my code too. Whether that works for you depends how much you like SQL, really.
– Tom Anderson
Feb 21 at 14:48
4
If you're going to put it in a utility method you might as well make it efficient.
– Todd Sewell
Feb 21 at 19:55
@ToddSewell, what do you mean?
– Gustavo Silva
Feb 22 at 12:12
4
@GustavoSilva Todd probably means that, this being a utility method of mine, there's no point in usingArrays.stream()when I can do the same with aforand a!= null, which is more efficient. And Todd would be right. However, when I coded this method I was looking for a way of doing this using Java 8 features, just like OP, so there's that.
– walen
Feb 22 at 12:23
3
@GustavoSilva Yeah that's basically it: if you're going to be putting this is a util function concerns about clean code aren't that important anymore, and so you might as well use a faster version.
– Todd Sewell
Feb 22 at 17:05
add a comment |
11
I use a helper function, something like
T firstNonNull<T>(T v0, T... vs) {
if(v0 != null)
return v0;
for(T x : vs) {
if (x != null)
return x;
}
return null;
}
Then this kind of code can be written as
String s = firstNonNull(str1, str2, str3, str4);
answered Feb 22 at 1:36
Michael AndersonMichael Anderson
45.9k696149
1
Why the extrav0parameter?
– tobias_k
Feb 23 at 10:08
1
@tobias_k The extra parameter when using varargs is the idiomatic way in Java to require 1 or more arguments rather than 0 or more. (See item 53 of Effective Java, Ed. 3., which usesminas an example.) I am less convinced that this is appropriate here.
– Nick
Feb 23 at 15:49
3
@Nick Yes, I guessed as much, but the function would work just as well (in fact behave exactly the same) without it.
– tobias_k
Feb 23 at 16:54
1
One of the key reasons for passing an extra first argument is to be explicit about the behaviour when passed an array. In this case, I wantfirstNonNull(arr)to return arr if it is not null. If it wasfirstNonNull(T... vs)it would instead return the first non-null entry in arr.
– Michael Anderson
Feb 24 at 12:09
add a comment |
3
A solution which can be applied to as many element as you want can be :
Stream.of(str1, str2, str3, str4)
.filter(Object::nonNull)
.findFirst()
.orElseThrow(IllegalArgumentException::new)
You could imagine a solution like below, but the first one ensures non nullity for all of the elements
Stream.of(str1, str2, str3).....orElse(str4)
answered Feb 21 at 6:52
azroazro
11.3k41638
5
orElsestr4inspite of it being a null actually
– nullpointer
Feb 21 at 6:53
@nullpointer OrorElseNull, which amounts to the same ifstr4is null.
– tobias_k
Feb 23 at 10:09
add a comment |
2
You can also lump up all the Strings into an array of String then do a for loop to check and break from the loop once it's assigned.
Assuming s1, s2, s3, s4 are all Strings.
String arrayOfStrings = {s1, s2, s3};
s = s4;
for (String value : arrayOfStrings) {
if (value != null) {
s = value;
break;
}
}
Edited to throw in condition for default to s4 if none is assigned.
answered Feb 21 at 7:00
Daniel ChewDaniel Chew
415
You have omitteds4(orstr4), which is to supposed be assigned tosin the end, even if it is null.
– displayName
Feb 22 at 16:36
add a comment |
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7 Answers
7
active
oldest
votes
7 Answers
7
active
oldest
votes
active
oldest
votes
active
oldest
votes
125
You may do it like so:
String s = Stream.of(str1, str2, str3)
.filter(Objects::nonNull)
.findFirst()
.orElse(str4);
edited Feb 22 at 8:57
Sulthan
97.4k16158202
answered Feb 21 at 6:51
Ravindra RanwalaRavindra Ranwala
10.6k42040
13
This. Think in what you need, not what you have.
– Thorbjørn Ravn Andersen
Feb 21 at 8:23
17
How much is the speed overhead? Creating Stream objects, calling 4 methods, creating temporary arrays ({str1, str2, str3}) look like much slower than a localifor?:, which the Java runtime can optimize. Is there some Stream-specific optimization injavacand the Java runtime which makes it as fast as?:? If not, I won't recommend this solution in performance-critical code.
– pts
Feb 21 at 9:58
13
@pts this is very likely to be slower than?:code and I'm sure you should avoid it in performance-critical code. It's however much more readable and you should recommend it in non-performance-critical code IMO, which I'm sure makes more than 99% of code.
– Aaron
Feb 21 at 10:39
34
Insert mandatory premature optimization comment.
– Sebastiaan van den Broek
Feb 21 at 12:31
17
Great solution! To increase readability a little bit I would suggest to addstr4to the parameters ofStream.of(...)and useorElse(null)in the end.
– danielp
Feb 21 at 23:12
|
show 4 more comments
125
You may do it like so:
String s = Stream.of(str1, str2, str3)
.filter(Objects::nonNull)
.findFirst()
.orElse(str4);
edited Feb 22 at 8:57
Sulthan
97.4k16158202
answered Feb 21 at 6:51
Ravindra RanwalaRavindra Ranwala
10.6k42040
13
This. Think in what you need, not what you have.
– Thorbjørn Ravn Andersen
Feb 21 at 8:23
17
How much is the speed overhead? Creating Stream objects, calling 4 methods, creating temporary arrays ({str1, str2, str3}) look like much slower than a localifor?:, which the Java runtime can optimize. Is there some Stream-specific optimization injavacand the Java runtime which makes it as fast as?:? If not, I won't recommend this solution in performance-critical code.
– pts
Feb 21 at 9:58
13
@pts this is very likely to be slower than?:code and I'm sure you should avoid it in performance-critical code. It's however much more readable and you should recommend it in non-performance-critical code IMO, which I'm sure makes more than 99% of code.
– Aaron
Feb 21 at 10:39
34
Insert mandatory premature optimization comment.
– Sebastiaan van den Broek
Feb 21 at 12:31
17
Great solution! To increase readability a little bit I would suggest to addstr4to the parameters ofStream.of(...)and useorElse(null)in the end.
– danielp
Feb 21 at 23:12
|
show 4 more comments
125
125
125
You may do it like so:
String s = Stream.of(str1, str2, str3)
.filter(Objects::nonNull)
.findFirst()
.orElse(str4);
edited Feb 22 at 8:57
Sulthan
97.4k16158202
answered Feb 21 at 6:51
Ravindra RanwalaRavindra Ranwala
10.6k42040
You may do it like so:
String s = Stream.of(str1, str2, str3)
.filter(Objects::nonNull)
.findFirst()
.orElse(str4);
edited Feb 22 at 8:57
Sulthan
97.4k16158202
answered Feb 21 at 6:51
Ravindra RanwalaRavindra Ranwala
10.6k42040
edited Feb 22 at 8:57
Sulthan
97.4k16158202
edited Feb 22 at 8:57
Sulthan
97.4k16158202
edited Feb 22 at 8:57
Sulthan
97.4k16158202
97.4k16158202
answered Feb 21 at 6:51
Ravindra RanwalaRavindra Ranwala
10.6k42040
answered Feb 21 at 6:51
Ravindra RanwalaRavindra Ranwala
10.6k42040
answered Feb 21 at 6:51
Ravindra RanwalaRavindra Ranwala
10.6k42040
10.6k42040
13
This. Think in what you need, not what you have.
– Thorbjørn Ravn Andersen
Feb 21 at 8:23
17
How much is the speed overhead? Creating Stream objects, calling 4 methods, creating temporary arrays ({str1, str2, str3}) look like much slower than a localifor?:, which the Java runtime can optimize. Is there some Stream-specific optimization injavacand the Java runtime which makes it as fast as?:? If not, I won't recommend this solution in performance-critical code.
– pts
Feb 21 at 9:58
13
@pts this is very likely to be slower than?:code and I'm sure you should avoid it in performance-critical code. It's however much more readable and you should recommend it in non-performance-critical code IMO, which I'm sure makes more than 99% of code.
– Aaron
Feb 21 at 10:39
34
Insert mandatory premature optimization comment.
– Sebastiaan van den Broek
Feb 21 at 12:31
17
Great solution! To increase readability a little bit I would suggest to addstr4to the parameters ofStream.of(...)and useorElse(null)in the end.
– danielp
Feb 21 at 23:12
|
show 4 more comments
13
This. Think in what you need, not what you have.
– Thorbjørn Ravn Andersen
Feb 21 at 8:23
17
How much is the speed overhead? Creating Stream objects, calling 4 methods, creating temporary arrays ({str1, str2, str3}) look like much slower than a localifor?:, which the Java runtime can optimize. Is there some Stream-specific optimization injavacand the Java runtime which makes it as fast as?:? If not, I won't recommend this solution in performance-critical code.
– pts
Feb 21 at 9:58
13
@pts this is very likely to be slower than?:code and I'm sure you should avoid it in performance-critical code. It's however much more readable and you should recommend it in non-performance-critical code IMO, which I'm sure makes more than 99% of code.
– Aaron
Feb 21 at 10:39
34
Insert mandatory premature optimization comment.
– Sebastiaan van den Broek
Feb 21 at 12:31
17
Great solution! To increase readability a little bit I would suggest to addstr4to the parameters ofStream.of(...)and useorElse(null)in the end.
– danielp
Feb 21 at 23:12
13
13
This. Think in what you need, not what you have.
– Thorbjørn Ravn Andersen
Feb 21 at 8:23
This. Think in what you need, not what you have.
– Thorbjørn Ravn Andersen
Feb 21 at 8:23
17
17
How much is the speed overhead? Creating Stream objects, calling 4 methods, creating temporary arrays (
{str1, str2, str3}) look like much slower than a local if or ?:, which the Java runtime can optimize. Is there some Stream-specific optimization in javac and the Java runtime which makes it as fast as ?:? If not, I won't recommend this solution in performance-critical code.– pts
Feb 21 at 9:58
How much is the speed overhead? Creating Stream objects, calling 4 methods, creating temporary arrays (
{str1, str2, str3}) look like much slower than a local if or ?:, which the Java runtime can optimize. Is there some Stream-specific optimization in javac and the Java runtime which makes it as fast as ?:? If not, I won't recommend this solution in performance-critical code.– pts
Feb 21 at 9:58
13
13
@pts this is very likely to be slower than
?: code and I'm sure you should avoid it in performance-critical code. It's however much more readable and you should recommend it in non-performance-critical code IMO, which I'm sure makes more than 99% of code.– Aaron
Feb 21 at 10:39
@pts this is very likely to be slower than
?: code and I'm sure you should avoid it in performance-critical code. It's however much more readable and you should recommend it in non-performance-critical code IMO, which I'm sure makes more than 99% of code.– Aaron
Feb 21 at 10:39
34
34
Insert mandatory premature optimization comment.
– Sebastiaan van den Broek
Feb 21 at 12:31
Insert mandatory premature optimization comment.
– Sebastiaan van den Broek
Feb 21 at 12:31
17
17
Great solution! To increase readability a little bit I would suggest to add
str4 to the parameters of Stream.of(...) and use orElse(null) in the end.– danielp
Feb 21 at 23:12
Great solution! To increase readability a little bit I would suggest to add
str4 to the parameters of Stream.of(...) and use orElse(null) in the end.– danielp
Feb 21 at 23:12
|
show 4 more comments
64
How about ternary conditional operator?
String s =
str1 != null ? str1 :
str2 != null ? str2 :
str3 != null ? str3 : str4
;
edited Feb 21 at 19:42
candied_orange
4,3221648
answered Feb 21 at 6:48
EranEran
287k37467556
47
actually, he's looking for "the best approach to do this in Java8". This approach can be used in Java8, so it all just depends on what the OP means by "the best", and on which grounds he bases the decision of what is better on.
– Stultuske
Feb 21 at 7:13
17
I usually dislike nested ternaries, but this looks pretty clean.
– JollyJoker
Feb 21 at 8:59
9
This is a huge pain to parse for anyone who isn't reading nested ternary operators every day.
– Cubic
Feb 21 at 15:46
1
@Cubic: If you think it's hard to parse, write a comment like// take first non-null of str1..3. Once you know what it does, it becomes easy to see how.
– Peter Cordes
Feb 22 at 3:36
4
@Cubic Yet, this is a simple repeated pattern. Once you parsed line 2, you've parsed the entire thing, no matter how many cases are included. And once you are done, you've learned to express a similar selection of ten different cases in a brief, and relatively simple manner. The next time you'll see a?:ladder, you'll know what it does. (Btw, functional programmers know this as(cond ...)clauses: It's always a guard followed by the appropriate value to use when the guard is true.)
– cmaster
Feb 22 at 17:18
|
show 1 more comment
64
How about ternary conditional operator?
String s =
str1 != null ? str1 :
str2 != null ? str2 :
str3 != null ? str3 : str4
;
edited Feb 21 at 19:42
candied_orange
4,3221648
answered Feb 21 at 6:48
EranEran
287k37467556
47
actually, he's looking for "the best approach to do this in Java8". This approach can be used in Java8, so it all just depends on what the OP means by "the best", and on which grounds he bases the decision of what is better on.
– Stultuske
Feb 21 at 7:13
17
I usually dislike nested ternaries, but this looks pretty clean.
– JollyJoker
Feb 21 at 8:59
9
This is a huge pain to parse for anyone who isn't reading nested ternary operators every day.
– Cubic
Feb 21 at 15:46
1
@Cubic: If you think it's hard to parse, write a comment like// take first non-null of str1..3. Once you know what it does, it becomes easy to see how.
– Peter Cordes
Feb 22 at 3:36
4
@Cubic Yet, this is a simple repeated pattern. Once you parsed line 2, you've parsed the entire thing, no matter how many cases are included. And once you are done, you've learned to express a similar selection of ten different cases in a brief, and relatively simple manner. The next time you'll see a?:ladder, you'll know what it does. (Btw, functional programmers know this as(cond ...)clauses: It's always a guard followed by the appropriate value to use when the guard is true.)
– cmaster
Feb 22 at 17:18
|
show 1 more comment
64
64
64
How about ternary conditional operator?
String s =
str1 != null ? str1 :
str2 != null ? str2 :
str3 != null ? str3 : str4
;
edited Feb 21 at 19:42
candied_orange
4,3221648
answered Feb 21 at 6:48
EranEran
287k37467556
How about ternary conditional operator?
String s =
str1 != null ? str1 :
str2 != null ? str2 :
str3 != null ? str3 : str4
;
edited Feb 21 at 19:42
candied_orange
4,3221648
answered Feb 21 at 6:48
EranEran
287k37467556
edited Feb 21 at 19:42
candied_orange
4,3221648
edited Feb 21 at 19:42
candied_orange
4,3221648
edited Feb 21 at 19:42
candied_orange
4,3221648
4,3221648
answered Feb 21 at 6:48
EranEran
287k37467556
answered Feb 21 at 6:48
EranEran
287k37467556
answered Feb 21 at 6:48
EranEran
287k37467556
287k37467556
47
actually, he's looking for "the best approach to do this in Java8". This approach can be used in Java8, so it all just depends on what the OP means by "the best", and on which grounds he bases the decision of what is better on.
– Stultuske
Feb 21 at 7:13
17
I usually dislike nested ternaries, but this looks pretty clean.
– JollyJoker
Feb 21 at 8:59
9
This is a huge pain to parse for anyone who isn't reading nested ternary operators every day.
– Cubic
Feb 21 at 15:46
1
@Cubic: If you think it's hard to parse, write a comment like// take first non-null of str1..3. Once you know what it does, it becomes easy to see how.
– Peter Cordes
Feb 22 at 3:36
4
@Cubic Yet, this is a simple repeated pattern. Once you parsed line 2, you've parsed the entire thing, no matter how many cases are included. And once you are done, you've learned to express a similar selection of ten different cases in a brief, and relatively simple manner. The next time you'll see a?:ladder, you'll know what it does. (Btw, functional programmers know this as(cond ...)clauses: It's always a guard followed by the appropriate value to use when the guard is true.)
– cmaster
Feb 22 at 17:18
|
show 1 more comment
47
actually, he's looking for "the best approach to do this in Java8". This approach can be used in Java8, so it all just depends on what the OP means by "the best", and on which grounds he bases the decision of what is better on.
– Stultuske
Feb 21 at 7:13
17
I usually dislike nested ternaries, but this looks pretty clean.
– JollyJoker
Feb 21 at 8:59
9
This is a huge pain to parse for anyone who isn't reading nested ternary operators every day.
– Cubic
Feb 21 at 15:46
1
@Cubic: If you think it's hard to parse, write a comment like// take first non-null of str1..3. Once you know what it does, it becomes easy to see how.
– Peter Cordes
Feb 22 at 3:36
4
@Cubic Yet, this is a simple repeated pattern. Once you parsed line 2, you've parsed the entire thing, no matter how many cases are included. And once you are done, you've learned to express a similar selection of ten different cases in a brief, and relatively simple manner. The next time you'll see a?:ladder, you'll know what it does. (Btw, functional programmers know this as(cond ...)clauses: It's always a guard followed by the appropriate value to use when the guard is true.)
– cmaster
Feb 22 at 17:18
47
47
actually, he's looking for "the best approach to do this in Java8". This approach can be used in Java8, so it all just depends on what the OP means by "the best", and on which grounds he bases the decision of what is better on.
– Stultuske
Feb 21 at 7:13
actually, he's looking for "the best approach to do this in Java8". This approach can be used in Java8, so it all just depends on what the OP means by "the best", and on which grounds he bases the decision of what is better on.
– Stultuske
Feb 21 at 7:13
17
17
I usually dislike nested ternaries, but this looks pretty clean.
– JollyJoker
Feb 21 at 8:59
I usually dislike nested ternaries, but this looks pretty clean.
– JollyJoker
Feb 21 at 8:59
9
9
This is a huge pain to parse for anyone who isn't reading nested ternary operators every day.
– Cubic
Feb 21 at 15:46
This is a huge pain to parse for anyone who isn't reading nested ternary operators every day.
– Cubic
Feb 21 at 15:46
1
1
@Cubic: If you think it's hard to parse, write a comment like
// take first non-null of str1..3. Once you know what it does, it becomes easy to see how.– Peter Cordes
Feb 22 at 3:36
@Cubic: If you think it's hard to parse, write a comment like
// take first non-null of str1..3. Once you know what it does, it becomes easy to see how.– Peter Cordes
Feb 22 at 3:36
4
4
@Cubic Yet, this is a simple repeated pattern. Once you parsed line 2, you've parsed the entire thing, no matter how many cases are included. And once you are done, you've learned to express a similar selection of ten different cases in a brief, and relatively simple manner. The next time you'll see a
?: ladder, you'll know what it does. (Btw, functional programmers know this as (cond ...) clauses: It's always a guard followed by the appropriate value to use when the guard is true.)– cmaster
Feb 22 at 17:18
@Cubic Yet, this is a simple repeated pattern. Once you parsed line 2, you've parsed the entire thing, no matter how many cases are included. And once you are done, you've learned to express a similar selection of ten different cases in a brief, and relatively simple manner. The next time you'll see a
?: ladder, you'll know what it does. (Btw, functional programmers know this as (cond ...) clauses: It's always a guard followed by the appropriate value to use when the guard is true.)– cmaster
Feb 22 at 17:18
|
show 1 more comment
28
You can also use a loop:
String strings = {str1, str2, str3, str4};
for(String str : strings) {
s = str;
if(s != null) break;
}
answered Feb 21 at 6:52
ernest_kernest_k
23.1k42647
add a comment |
28
You can also use a loop:
String strings = {str1, str2, str3, str4};
for(String str : strings) {
s = str;
if(s != null) break;
}
answered Feb 21 at 6:52
ernest_kernest_k
23.1k42647
add a comment |
28
28
28
You can also use a loop:
String strings = {str1, str2, str3, str4};
for(String str : strings) {
s = str;
if(s != null) break;
}
answered Feb 21 at 6:52
ernest_kernest_k
23.1k42647
You can also use a loop:
String strings = {str1, str2, str3, str4};
for(String str : strings) {
s = str;
if(s != null) break;
}
answered Feb 21 at 6:52
ernest_kernest_k
23.1k42647
answered Feb 21 at 6:52
ernest_kernest_k
23.1k42647
answered Feb 21 at 6:52
ernest_kernest_k
23.1k42647
answered Feb 21 at 6:52
ernest_kernest_k
23.1k42647
23.1k42647
add a comment |
add a comment |
20
Current answers are nice but you really should put that in a utility method:
public static Optional<String> firstNonNull(String... strings) {
return Arrays.stream(strings)
.filter(Objects::nonNull)
.findFirst();
}
That method has been in my Util class for years, makes code much cleaner:
String s = firstNonNull(str1, str2, str3).orElse(str4);
You can even make it generic:
public static <T> Optional<T> firstNonNull(T... objects) {
return Arrays.stream(objects)
.filter(Objects::nonNull)
.findFirst();
}
// Use
Student student = firstNonNull(student1, student2, student3).orElseGet(Student::new);
answered Feb 21 at 8:51
walenwalen
3,87211539
8
FWIW, in SQL, this function is called coalesce, so i call it that in my code too. Whether that works for you depends how much you like SQL, really.
– Tom Anderson
Feb 21 at 14:48
4
If you're going to put it in a utility method you might as well make it efficient.
– Todd Sewell
Feb 21 at 19:55
@ToddSewell, what do you mean?
– Gustavo Silva
Feb 22 at 12:12
4
@GustavoSilva Todd probably means that, this being a utility method of mine, there's no point in usingArrays.stream()when I can do the same with aforand a!= null, which is more efficient. And Todd would be right. However, when I coded this method I was looking for a way of doing this using Java 8 features, just like OP, so there's that.
– walen
Feb 22 at 12:23
3
@GustavoSilva Yeah that's basically it: if you're going to be putting this is a util function concerns about clean code aren't that important anymore, and so you might as well use a faster version.
– Todd Sewell
Feb 22 at 17:05
add a comment |
20
Current answers are nice but you really should put that in a utility method:
public static Optional<String> firstNonNull(String... strings) {
return Arrays.stream(strings)
.filter(Objects::nonNull)
.findFirst();
}
That method has been in my Util class for years, makes code much cleaner:
String s = firstNonNull(str1, str2, str3).orElse(str4);
You can even make it generic:
public static <T> Optional<T> firstNonNull(T... objects) {
return Arrays.stream(objects)
.filter(Objects::nonNull)
.findFirst();
}
// Use
Student student = firstNonNull(student1, student2, student3).orElseGet(Student::new);
answered Feb 21 at 8:51
walenwalen
3,87211539
8
FWIW, in SQL, this function is called coalesce, so i call it that in my code too. Whether that works for you depends how much you like SQL, really.
– Tom Anderson
Feb 21 at 14:48
4
If you're going to put it in a utility method you might as well make it efficient.
– Todd Sewell
Feb 21 at 19:55
@ToddSewell, what do you mean?
– Gustavo Silva
Feb 22 at 12:12
4
@GustavoSilva Todd probably means that, this being a utility method of mine, there's no point in usingArrays.stream()when I can do the same with aforand a!= null, which is more efficient. And Todd would be right. However, when I coded this method I was looking for a way of doing this using Java 8 features, just like OP, so there's that.
– walen
Feb 22 at 12:23
3
@GustavoSilva Yeah that's basically it: if you're going to be putting this is a util function concerns about clean code aren't that important anymore, and so you might as well use a faster version.
– Todd Sewell
Feb 22 at 17:05
add a comment |
20
20
20
Current answers are nice but you really should put that in a utility method:
public static Optional<String> firstNonNull(String... strings) {
return Arrays.stream(strings)
.filter(Objects::nonNull)
.findFirst();
}
That method has been in my Util class for years, makes code much cleaner:
String s = firstNonNull(str1, str2, str3).orElse(str4);
You can even make it generic:
public static <T> Optional<T> firstNonNull(T... objects) {
return Arrays.stream(objects)
.filter(Objects::nonNull)
.findFirst();
}
// Use
Student student = firstNonNull(student1, student2, student3).orElseGet(Student::new);
answered Feb 21 at 8:51
walenwalen
3,87211539
Current answers are nice but you really should put that in a utility method:
public static Optional<String> firstNonNull(String... strings) {
return Arrays.stream(strings)
.filter(Objects::nonNull)
.findFirst();
}
That method has been in my Util class for years, makes code much cleaner:
String s = firstNonNull(str1, str2, str3).orElse(str4);
You can even make it generic:
public static <T> Optional<T> firstNonNull(T... objects) {
return Arrays.stream(objects)
.filter(Objects::nonNull)
.findFirst();
}
// Use
Student student = firstNonNull(student1, student2, student3).orElseGet(Student::new);
answered Feb 21 at 8:51
walenwalen
3,87211539
edited Feb 21 at 9:10
answered Feb 21 at 8:51
walenwalen
3,87211539
answered Feb 21 at 8:51
walenwalen
3,87211539
answered Feb 21 at 8:51
walenwalen
3,87211539
3,87211539
8
FWIW, in SQL, this function is called coalesce, so i call it that in my code too. Whether that works for you depends how much you like SQL, really.
– Tom Anderson
Feb 21 at 14:48
4
If you're going to put it in a utility method you might as well make it efficient.
– Todd Sewell
Feb 21 at 19:55
@ToddSewell, what do you mean?
– Gustavo Silva
Feb 22 at 12:12
4
@GustavoSilva Todd probably means that, this being a utility method of mine, there's no point in usingArrays.stream()when I can do the same with aforand a!= null, which is more efficient. And Todd would be right. However, when I coded this method I was looking for a way of doing this using Java 8 features, just like OP, so there's that.
– walen
Feb 22 at 12:23
3
@GustavoSilva Yeah that's basically it: if you're going to be putting this is a util function concerns about clean code aren't that important anymore, and so you might as well use a faster version.
– Todd Sewell
Feb 22 at 17:05
add a comment |
8
FWIW, in SQL, this function is called coalesce, so i call it that in my code too. Whether that works for you depends how much you like SQL, really.
– Tom Anderson
Feb 21 at 14:48
4
If you're going to put it in a utility method you might as well make it efficient.
– Todd Sewell
Feb 21 at 19:55
@ToddSewell, what do you mean?
– Gustavo Silva
Feb 22 at 12:12
4
@GustavoSilva Todd probably means that, this being a utility method of mine, there's no point in usingArrays.stream()when I can do the same with aforand a!= null, which is more efficient. And Todd would be right. However, when I coded this method I was looking for a way of doing this using Java 8 features, just like OP, so there's that.
– walen
Feb 22 at 12:23
3
@GustavoSilva Yeah that's basically it: if you're going to be putting this is a util function concerns about clean code aren't that important anymore, and so you might as well use a faster version.
– Todd Sewell
Feb 22 at 17:05
8
8
FWIW, in SQL, this function is called coalesce, so i call it that in my code too. Whether that works for you depends how much you like SQL, really.
– Tom Anderson
Feb 21 at 14:48
FWIW, in SQL, this function is called coalesce, so i call it that in my code too. Whether that works for you depends how much you like SQL, really.
– Tom Anderson
Feb 21 at 14:48
4
4
If you're going to put it in a utility method you might as well make it efficient.
– Todd Sewell
Feb 21 at 19:55
If you're going to put it in a utility method you might as well make it efficient.
– Todd Sewell
Feb 21 at 19:55
@ToddSewell, what do you mean?
– Gustavo Silva
Feb 22 at 12:12
@ToddSewell, what do you mean?
– Gustavo Silva
Feb 22 at 12:12
4
4
@GustavoSilva Todd probably means that, this being a utility method of mine, there's no point in using
Arrays.stream() when I can do the same with a for and a != null, which is more efficient. And Todd would be right. However, when I coded this method I was looking for a way of doing this using Java 8 features, just like OP, so there's that.– walen
Feb 22 at 12:23
@GustavoSilva Todd probably means that, this being a utility method of mine, there's no point in using
Arrays.stream() when I can do the same with a for and a != null, which is more efficient. And Todd would be right. However, when I coded this method I was looking for a way of doing this using Java 8 features, just like OP, so there's that.– walen
Feb 22 at 12:23
3
3
@GustavoSilva Yeah that's basically it: if you're going to be putting this is a util function concerns about clean code aren't that important anymore, and so you might as well use a faster version.
– Todd Sewell
Feb 22 at 17:05
@GustavoSilva Yeah that's basically it: if you're going to be putting this is a util function concerns about clean code aren't that important anymore, and so you might as well use a faster version.
– Todd Sewell
Feb 22 at 17:05
add a comment |
11
I use a helper function, something like
T firstNonNull<T>(T v0, T... vs) {
if(v0 != null)
return v0;
for(T x : vs) {
if (x != null)
return x;
}
return null;
}
Then this kind of code can be written as
String s = firstNonNull(str1, str2, str3, str4);
answered Feb 22 at 1:36
Michael AndersonMichael Anderson
45.9k696149
1
Why the extrav0parameter?
– tobias_k
Feb 23 at 10:08
1
@tobias_k The extra parameter when using varargs is the idiomatic way in Java to require 1 or more arguments rather than 0 or more. (See item 53 of Effective Java, Ed. 3., which usesminas an example.) I am less convinced that this is appropriate here.
– Nick
Feb 23 at 15:49
3
@Nick Yes, I guessed as much, but the function would work just as well (in fact behave exactly the same) without it.
– tobias_k
Feb 23 at 16:54
1
One of the key reasons for passing an extra first argument is to be explicit about the behaviour when passed an array. In this case, I wantfirstNonNull(arr)to return arr if it is not null. If it wasfirstNonNull(T... vs)it would instead return the first non-null entry in arr.
– Michael Anderson
Feb 24 at 12:09
add a comment |
11
I use a helper function, something like
T firstNonNull<T>(T v0, T... vs) {
if(v0 != null)
return v0;
for(T x : vs) {
if (x != null)
return x;
}
return null;
}
Then this kind of code can be written as
String s = firstNonNull(str1, str2, str3, str4);
answered Feb 22 at 1:36
Michael AndersonMichael Anderson
45.9k696149
1
Why the extrav0parameter?
– tobias_k
Feb 23 at 10:08
1
@tobias_k The extra parameter when using varargs is the idiomatic way in Java to require 1 or more arguments rather than 0 or more. (See item 53 of Effective Java, Ed. 3., which usesminas an example.) I am less convinced that this is appropriate here.
– Nick
Feb 23 at 15:49
3
@Nick Yes, I guessed as much, but the function would work just as well (in fact behave exactly the same) without it.
– tobias_k
Feb 23 at 16:54
1
One of the key reasons for passing an extra first argument is to be explicit about the behaviour when passed an array. In this case, I wantfirstNonNull(arr)to return arr if it is not null. If it wasfirstNonNull(T... vs)it would instead return the first non-null entry in arr.
– Michael Anderson
Feb 24 at 12:09
add a comment |
11
11
11
I use a helper function, something like
T firstNonNull<T>(T v0, T... vs) {
if(v0 != null)
return v0;
for(T x : vs) {
if (x != null)
return x;
}
return null;
}
Then this kind of code can be written as
String s = firstNonNull(str1, str2, str3, str4);
answered Feb 22 at 1:36
Michael AndersonMichael Anderson
45.9k696149
I use a helper function, something like
T firstNonNull<T>(T v0, T... vs) {
if(v0 != null)
return v0;
for(T x : vs) {
if (x != null)
return x;
}
return null;
}
Then this kind of code can be written as
String s = firstNonNull(str1, str2, str3, str4);
answered Feb 22 at 1:36
Michael AndersonMichael Anderson
45.9k696149
answered Feb 22 at 1:36
Michael AndersonMichael Anderson
45.9k696149
answered Feb 22 at 1:36
Michael AndersonMichael Anderson
45.9k696149
answered Feb 22 at 1:36
Michael AndersonMichael Anderson
45.9k696149
45.9k696149
1
Why the extrav0parameter?
– tobias_k
Feb 23 at 10:08
1
@tobias_k The extra parameter when using varargs is the idiomatic way in Java to require 1 or more arguments rather than 0 or more. (See item 53 of Effective Java, Ed. 3., which usesminas an example.) I am less convinced that this is appropriate here.
– Nick
Feb 23 at 15:49
3
@Nick Yes, I guessed as much, but the function would work just as well (in fact behave exactly the same) without it.
– tobias_k
Feb 23 at 16:54
1
One of the key reasons for passing an extra first argument is to be explicit about the behaviour when passed an array. In this case, I wantfirstNonNull(arr)to return arr if it is not null. If it wasfirstNonNull(T... vs)it would instead return the first non-null entry in arr.
– Michael Anderson
Feb 24 at 12:09
add a comment |
1
Why the extrav0parameter?
– tobias_k
Feb 23 at 10:08
1
@tobias_k The extra parameter when using varargs is the idiomatic way in Java to require 1 or more arguments rather than 0 or more. (See item 53 of Effective Java, Ed. 3., which usesminas an example.) I am less convinced that this is appropriate here.
– Nick
Feb 23 at 15:49
3
@Nick Yes, I guessed as much, but the function would work just as well (in fact behave exactly the same) without it.
– tobias_k
Feb 23 at 16:54
1
One of the key reasons for passing an extra first argument is to be explicit about the behaviour when passed an array. In this case, I wantfirstNonNull(arr)to return arr if it is not null. If it wasfirstNonNull(T... vs)it would instead return the first non-null entry in arr.
– Michael Anderson
Feb 24 at 12:09
1
1
Why the extra
v0 parameter?– tobias_k
Feb 23 at 10:08
Why the extra
v0 parameter?– tobias_k
Feb 23 at 10:08
1
1
@tobias_k The extra parameter when using varargs is the idiomatic way in Java to require 1 or more arguments rather than 0 or more. (See item 53 of Effective Java, Ed. 3., which uses
min as an example.) I am less convinced that this is appropriate here.– Nick
Feb 23 at 15:49
@tobias_k The extra parameter when using varargs is the idiomatic way in Java to require 1 or more arguments rather than 0 or more. (See item 53 of Effective Java, Ed. 3., which uses
min as an example.) I am less convinced that this is appropriate here.– Nick
Feb 23 at 15:49
3
3
@Nick Yes, I guessed as much, but the function would work just as well (in fact behave exactly the same) without it.
– tobias_k
Feb 23 at 16:54
@Nick Yes, I guessed as much, but the function would work just as well (in fact behave exactly the same) without it.
– tobias_k
Feb 23 at 16:54
1
1
One of the key reasons for passing an extra first argument is to be explicit about the behaviour when passed an array. In this case, I want
firstNonNull(arr) to return arr if it is not null. If it was firstNonNull(T... vs) it would instead return the first non-null entry in arr.– Michael Anderson
Feb 24 at 12:09
One of the key reasons for passing an extra first argument is to be explicit about the behaviour when passed an array. In this case, I want
firstNonNull(arr) to return arr if it is not null. If it was firstNonNull(T... vs) it would instead return the first non-null entry in arr.– Michael Anderson
Feb 24 at 12:09
add a comment |
3
A solution which can be applied to as many element as you want can be :
Stream.of(str1, str2, str3, str4)
.filter(Object::nonNull)
.findFirst()
.orElseThrow(IllegalArgumentException::new)
You could imagine a solution like below, but the first one ensures non nullity for all of the elements
Stream.of(str1, str2, str3).....orElse(str4)
answered Feb 21 at 6:52
azroazro
11.3k41638
5
orElsestr4inspite of it being a null actually
– nullpointer
Feb 21 at 6:53
@nullpointer OrorElseNull, which amounts to the same ifstr4is null.
– tobias_k
Feb 23 at 10:09
add a comment |
3
A solution which can be applied to as many element as you want can be :
Stream.of(str1, str2, str3, str4)
.filter(Object::nonNull)
.findFirst()
.orElseThrow(IllegalArgumentException::new)
You could imagine a solution like below, but the first one ensures non nullity for all of the elements
Stream.of(str1, str2, str3).....orElse(str4)
answered Feb 21 at 6:52
azroazro
11.3k41638
5
orElsestr4inspite of it being a null actually
– nullpointer
Feb 21 at 6:53
@nullpointer OrorElseNull, which amounts to the same ifstr4is null.
– tobias_k
Feb 23 at 10:09
add a comment |
3
3
3
A solution which can be applied to as many element as you want can be :
Stream.of(str1, str2, str3, str4)
.filter(Object::nonNull)
.findFirst()
.orElseThrow(IllegalArgumentException::new)
You could imagine a solution like below, but the first one ensures non nullity for all of the elements
Stream.of(str1, str2, str3).....orElse(str4)
answered Feb 21 at 6:52
azroazro
11.3k41638
A solution which can be applied to as many element as you want can be :
Stream.of(str1, str2, str3, str4)
.filter(Object::nonNull)
.findFirst()
.orElseThrow(IllegalArgumentException::new)
You could imagine a solution like below, but the first one ensures non nullity for all of the elements
Stream.of(str1, str2, str3).....orElse(str4)
answered Feb 21 at 6:52
azroazro
11.3k41638
answered Feb 21 at 6:52
azroazro
11.3k41638
answered Feb 21 at 6:52
azroazro
11.3k41638
answered Feb 21 at 6:52
azroazro
11.3k41638
11.3k41638
5
orElsestr4inspite of it being a null actually
– nullpointer
Feb 21 at 6:53
@nullpointer OrorElseNull, which amounts to the same ifstr4is null.
– tobias_k
Feb 23 at 10:09
add a comment |
5
orElsestr4inspite of it being a null actually
– nullpointer
Feb 21 at 6:53
@nullpointer OrorElseNull, which amounts to the same ifstr4is null.
– tobias_k
Feb 23 at 10:09
5
5
orElse
str4 inspite of it being a null actually– nullpointer
Feb 21 at 6:53
orElse
str4 inspite of it being a null actually– nullpointer
Feb 21 at 6:53
@nullpointer Or
orElseNull, which amounts to the same if str4 is null.– tobias_k
Feb 23 at 10:09
@nullpointer Or
orElseNull, which amounts to the same if str4 is null.– tobias_k
Feb 23 at 10:09
add a comment |
2
You can also lump up all the Strings into an array of String then do a for loop to check and break from the loop once it's assigned.
Assuming s1, s2, s3, s4 are all Strings.
String arrayOfStrings = {s1, s2, s3};
s = s4;
for (String value : arrayOfStrings) {
if (value != null) {
s = value;
break;
}
}
Edited to throw in condition for default to s4 if none is assigned.
answered Feb 21 at 7:00
Daniel ChewDaniel Chew
415
You have omitteds4(orstr4), which is to supposed be assigned tosin the end, even if it is null.
– displayName
Feb 22 at 16:36
add a comment |
2
You can also lump up all the Strings into an array of String then do a for loop to check and break from the loop once it's assigned.
Assuming s1, s2, s3, s4 are all Strings.
String arrayOfStrings = {s1, s2, s3};
s = s4;
for (String value : arrayOfStrings) {
if (value != null) {
s = value;
break;
}
}
Edited to throw in condition for default to s4 if none is assigned.
answered Feb 21 at 7:00
Daniel ChewDaniel Chew
415
You have omitteds4(orstr4), which is to supposed be assigned tosin the end, even if it is null.
– displayName
Feb 22 at 16:36
add a comment |
2
2
2
You can also lump up all the Strings into an array of String then do a for loop to check and break from the loop once it's assigned.
Assuming s1, s2, s3, s4 are all Strings.
String arrayOfStrings = {s1, s2, s3};
s = s4;
for (String value : arrayOfStrings) {
if (value != null) {
s = value;
break;
}
}
Edited to throw in condition for default to s4 if none is assigned.
answered Feb 21 at 7:00
Daniel ChewDaniel Chew
415
You can also lump up all the Strings into an array of String then do a for loop to check and break from the loop once it's assigned.
Assuming s1, s2, s3, s4 are all Strings.
String arrayOfStrings = {s1, s2, s3};
s = s4;
for (String value : arrayOfStrings) {
if (value != null) {
s = value;
break;
}
}
Edited to throw in condition for default to s4 if none is assigned.
answered Feb 21 at 7:00
Daniel ChewDaniel Chew
415
edited Feb 23 at 18:20
answered Feb 21 at 7:00
Daniel ChewDaniel Chew
415
answered Feb 21 at 7:00
Daniel ChewDaniel Chew
415
answered Feb 21 at 7:00
Daniel ChewDaniel Chew
415
415
You have omitteds4(orstr4), which is to supposed be assigned tosin the end, even if it is null.
– displayName
Feb 22 at 16:36
add a comment |
You have omitteds4(orstr4), which is to supposed be assigned tosin the end, even if it is null.
– displayName
Feb 22 at 16:36
You have omitted
s4 (or str4), which is to supposed be assigned to s in the end, even if it is null.– displayName
Feb 22 at 16:36
You have omitted
s4 (or str4), which is to supposed be assigned to s in the end, even if it is null.– displayName
Feb 22 at 16:36
add a comment |
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3
Java9
orsyntaxString s = Optional.ofNullable(str1) .or(() -> Optional.ofNullable(str2)) .or(() -> Optional.ofNullable(str3)) .orElse(str4);looks not as good as theStream.ofI would sya.– nullpointer
Feb 21 at 6:55
1
@OleV.V. Nothing wrong, the OP is already aware of it and is seeking something specific to Java-8.
– nullpointer
Feb 21 at 8:12
2
I know the user is asking for Java-8 specific solution, but on a general note, I would go with
StringUtils.firstNonBlank()– Mohamed Anees A
Feb 21 at 12:09
2
Problem is, Java 8/streams isn't the best solution for this. That code really smells like a refactor is in order but without more context it's really hard to tell. For starters--why aren't three objects that are probably so closely related not already in a collection?
– Bill K
Feb 21 at 17:49
1
@MohamedAneesA would have provided the best answer (as a comment) but didn't specify the source of StringUtils in this case. At any rate, if you HAVE to have these as a bunch of separate strings, coding it as a vargs method like "firstNonBlank" is ideal, the syntax inside will be an array making a simple for-each loop with a return on finding a non-null value trivial and obvious. In this case, java 8 streams are an attractive nuisance. they tempt you to inline and complicate something that should be a simple method/loop.
– Bill K
Feb 21 at 17:55