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multiple null checks in Java8

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17

4

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

share|improve this question

edited 5 hours ago

azro

11.2k41638

asked 5 hours ago

sparkersparker

423515

• 
  
  
  

  
  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
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Optional.ofNullable is in Java-8 only, i guess.
  
  – Common Man
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @OleV.V. Nothing wrong, the OP is already aware of it and is seeking something specific to Java-8.
  
  – nullpointer
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This was what the elvis operator should do easily. I think it is a good thing it wasn't introduced as it makes it easier to work with null values which I think is the wrong way to go.
  
  – Thorbjørn Ravn Andersen
  3 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  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
  12 mins ago
  

  
  
  
  

add a comment | 

17

4

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

share|improve this question

edited 5 hours ago

azro

11.2k41638

asked 5 hours ago

sparkersparker

423515

• 
  
  
  

  
  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
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Optional.ofNullable is in Java-8 only, i guess.
  
  – Common Man
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @OleV.V. Nothing wrong, the OP is already aware of it and is seeking something specific to Java-8.
  
  – nullpointer
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This was what the elvis operator should do easily. I think it is a good thing it wasn't introduced as it makes it easier to work with null values which I think is the wrong way to go.
  
  – Thorbjørn Ravn Andersen
  3 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  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
  12 mins ago
  

  
  
  
  

add a comment | 

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

share|improve this question

edited 5 hours ago

azro

11.2k41638

asked 5 hours ago

sparkersparker

423515

String s = null;



if(str1 != null) {

    s = str1;

} else if(str2 != null) {

    s=str2;

}else if(str3 != null) {

    s=str3;

}else{

    s = str4;

}

String s = Optional.ofNullable(str1)

                   .orElse(Optional.ofNullable(str2)

                                   .orElse(Optional.ofNullable(str3)

                                                   .orElse(str4)));

share|improve this question

edited 5 hours ago

azro

11.2k41638

asked 5 hours ago

sparkersparker

423515

share|improve this question

edited 5 hours ago

azro

11.2k41638

asked 5 hours ago

sparkersparker

423515

edited 5 hours ago

azro

11.2k41638

edited 5 hours ago

azro

11.2k41638

asked 5 hours ago

sparkersparker

423515

asked 5 hours ago

sparkersparker

423515

6 Answers
6

active

oldest

votes

30

You may do it like so:

String s = Stream.of(str1, str2, str3)

                 .filter(Objects::nonNull)

                 .findFirst()

                 .orElse(str4);

share|improve this answer

edited 5 hours ago

nullpointer

42.5k10101195

answered 5 hours ago

Ravindra RanwalaRavindra Ranwala

9,81231737

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  This. Think in what you need, not what you have.
  
  – Thorbjørn Ravn Andersen
  3 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  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
  2 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @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
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @pts There are no Stream specific optimizations, neither in javac nor in the runtime. This does not preclude the general optimizations, like inlining all of the code, followed by eliminating redundant operations. In principle, the end result could be as efficient as the plain conditional expressions, however, it’s rather unlikely that it ever gets there, as the runtime would spend the necessary effort only on the hottest code paths.
  
  – Holger
  1 hour ago
  
  
  

  
  
  
  

add a comment | 

10

How about ternary conditional operator?

String s = str1 != null ? str1 : str2 != null ? str2 : str3 != null ? str3 : str4;

share|improve this answer

answered 5 hours ago

EranEran

286k37466554

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  is it java 8 code ?
  
  – Arun Kumar
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @ArunKumar I believe you know it isn't.. It works in Java 8 (and prior versions), though.
  
  – Eran
  5 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  in question solution already posted for <8 ...user is asking for java 8..
  
  – Arun Kumar
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  11
  

  
  
  
  
  
  

  
  
  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
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I usually dislike nested ternaries, but this looks pretty clean.
  
  – JollyJoker
  3 hours ago
  

  
  
  
  

add a comment | 

2

You can also use a loop:

String[] strings = {str1, str2, str3, str4};

for(String str : strings) {

    s = str;

    if(s != null) break;

}

share|improve this answer

answered 5 hours ago

ernest_kernest_k

22.6k42546

add a comment | 

1

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)

share|improve this answer

answered 5 hours ago

azroazro

11.2k41638

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  orElse str4 inspite of it being a null actually
  
  – nullpointer
  5 hours ago
  

  
  
  
  

add a comment | 

1

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);

share|improve this answer

edited 3 hours ago

answered 3 hours ago

walenwalen

3,66211538

add a comment | 

0

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 are all Strings.

String[] arrayOfStrings = {s1, s2, s3};



for (String value : arrayOfStrings) {

    if (value != null) { 

        s = value;

        break;

    }

}

share|improve this answer

answered 5 hours ago

Daniel ChewDaniel Chew

13

add a comment | 

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30

You may do it like so:

String s = Stream.of(str1, str2, str3)

                 .filter(Objects::nonNull)

                 .findFirst()

                 .orElse(str4);

share|improve this answer

edited 5 hours ago

nullpointer

42.5k10101195

answered 5 hours ago

Ravindra RanwalaRavindra Ranwala

9,81231737

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  This. Think in what you need, not what you have.
  
  – Thorbjørn Ravn Andersen
  3 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  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
  2 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @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
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @pts There are no Stream specific optimizations, neither in javac nor in the runtime. This does not preclude the general optimizations, like inlining all of the code, followed by eliminating redundant operations. In principle, the end result could be as efficient as the plain conditional expressions, however, it’s rather unlikely that it ever gets there, as the runtime would spend the necessary effort only on the hottest code paths.
  
  – Holger
  1 hour ago
  
  
  

  
  
  
  

add a comment | 

30

You may do it like so:

String s = Stream.of(str1, str2, str3)

                 .filter(Objects::nonNull)

                 .findFirst()

                 .orElse(str4);

share|improve this answer

edited 5 hours ago

nullpointer

42.5k10101195

answered 5 hours ago

Ravindra RanwalaRavindra Ranwala

9,81231737

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  This. Think in what you need, not what you have.
  
  – Thorbjørn Ravn Andersen
  3 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  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
  2 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @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
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @pts There are no Stream specific optimizations, neither in javac nor in the runtime. This does not preclude the general optimizations, like inlining all of the code, followed by eliminating redundant operations. In principle, the end result could be as efficient as the plain conditional expressions, however, it’s rather unlikely that it ever gets there, as the runtime would spend the necessary effort only on the hottest code paths.
  
  – Holger
  1 hour ago
  
  
  

  
  
  
  

add a comment | 

You may do it like so:

String s = Stream.of(str1, str2, str3)

                 .filter(Objects::nonNull)

                 .findFirst()

                 .orElse(str4);

share|improve this answer

edited 5 hours ago

nullpointer

42.5k10101195

answered 5 hours ago

Ravindra RanwalaRavindra Ranwala

9,81231737

String s = Stream.of(str1, str2, str3)

                 .filter(Objects::nonNull)

                 .findFirst()

                 .orElse(str4);

share|improve this answer

edited 5 hours ago

nullpointer

42.5k10101195

answered 5 hours ago

Ravindra RanwalaRavindra Ranwala

9,81231737

edited 5 hours ago

nullpointer

42.5k10101195

edited 5 hours ago

nullpointer

42.5k10101195

answered 5 hours ago

Ravindra RanwalaRavindra Ranwala

9,81231737

answered 5 hours ago

Ravindra RanwalaRavindra Ranwala

9,81231737

10

How about ternary conditional operator?

String s = str1 != null ? str1 : str2 != null ? str2 : str3 != null ? str3 : str4;

share|improve this answer

answered 5 hours ago

EranEran

286k37466554

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  is it java 8 code ?
  
  – Arun Kumar
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @ArunKumar I believe you know it isn't.. It works in Java 8 (and prior versions), though.
  
  – Eran
  5 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  in question solution already posted for <8 ...user is asking for java 8..
  
  – Arun Kumar
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  11
  

  
  
  
  
  
  

  
  
  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
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I usually dislike nested ternaries, but this looks pretty clean.
  
  – JollyJoker
  3 hours ago
  

  
  
  
  

add a comment | 

10

How about ternary conditional operator?

String s = str1 != null ? str1 : str2 != null ? str2 : str3 != null ? str3 : str4;

share|improve this answer

answered 5 hours ago

EranEran

286k37466554

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  is it java 8 code ?
  
  – Arun Kumar
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @ArunKumar I believe you know it isn't.. It works in Java 8 (and prior versions), though.
  
  – Eran
  5 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  in question solution already posted for <8 ...user is asking for java 8..
  
  – Arun Kumar
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  11
  

  
  
  
  
  
  

  
  
  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
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I usually dislike nested ternaries, but this looks pretty clean.
  
  – JollyJoker
  3 hours ago
  

  
  
  
  

add a comment | 

How about ternary conditional operator?

String s = str1 != null ? str1 : str2 != null ? str2 : str3 != null ? str3 : str4;

share|improve this answer

answered 5 hours ago

EranEran

286k37466554

String s = str1 != null ? str1 : str2 != null ? str2 : str3 != null ? str3 : str4;

share|improve this answer

answered 5 hours ago

EranEran

286k37466554

answered 5 hours ago

EranEran

286k37466554

answered 5 hours ago

EranEran

286k37466554

2

You can also use a loop:

String[] strings = {str1, str2, str3, str4};

for(String str : strings) {

    s = str;

    if(s != null) break;

}

share|improve this answer

answered 5 hours ago

ernest_kernest_k

22.6k42546

add a comment | 

2

You can also use a loop:

String[] strings = {str1, str2, str3, str4};

for(String str : strings) {

    s = str;

    if(s != null) break;

}

share|improve this answer

answered 5 hours ago

ernest_kernest_k

22.6k42546

add a comment | 

You can also use a loop:

String[] strings = {str1, str2, str3, str4};

for(String str : strings) {

    s = str;

    if(s != null) break;

}

share|improve this answer

answered 5 hours ago

ernest_kernest_k

22.6k42546

String[] strings = {str1, str2, str3, str4};

for(String str : strings) {

    s = str;

    if(s != null) break;

}

share|improve this answer

answered 5 hours ago

ernest_kernest_k

22.6k42546

answered 5 hours ago

ernest_kernest_k

22.6k42546

answered 5 hours ago

ernest_kernest_k

22.6k42546

1

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)

share|improve this answer

answered 5 hours ago

azroazro

11.2k41638

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  orElse str4 inspite of it being a null actually
  
  – nullpointer
  5 hours ago
  

  
  
  
  

add a comment | 

1

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)

share|improve this answer

answered 5 hours ago

azroazro

11.2k41638

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  orElse str4 inspite of it being a null actually
  
  – nullpointer
  5 hours ago
  

  
  
  
  

add a comment | 

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)

share|improve this answer

answered 5 hours ago

azroazro

11.2k41638

Stream.of(str1, str2, str3, str4)

      .filter(Object::nonNull)

      .findFirst()

      .orElseThrow(IllegalArgumentException::new)

Stream.of(str1, str2, str3).....orElse(str4)

share|improve this answer

answered 5 hours ago

azroazro

11.2k41638

answered 5 hours ago

azroazro

11.2k41638

answered 5 hours ago

azroazro

11.2k41638

1

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);

share|improve this answer

edited 3 hours ago

answered 3 hours ago

walenwalen

3,66211538

add a comment | 

1

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);

share|improve this answer

edited 3 hours ago

answered 3 hours ago

walenwalen

3,66211538

add a comment | 

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);

share|improve this answer

edited 3 hours ago

answered 3 hours ago

walenwalen

3,66211538

public static Optional<String> firstNonNull(String... strings) {

    return Arrays.stream(strings)

            .filter(Objects::nonNull)

            .findFirst();

}

String s = firstNonNull(str1, str2, str3).orElse(str4);

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);