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Using streams for a null-safe conversion from an array to list

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9

1

I'm looking for a succinct way to rewrite a piece of Java code so that it uses streams to convert an array to a list in a null-safe fashion. Here's the original code:

public MailObject toMailObject(final String[] ccAddresses) 
 final MailObject mailObject = new MailObject();

 // line of code to be altered
 mailObject.setCcAddresses(ccAddresses == null 
 ? Collections.emptyList() : Arrays.asList(ccAddresses));

 // other necessary code

 return mailObject;

I've thought of doing something like this:

// psuedocode that obviously doesn't compile
Optional.ofNullable(ccAddresses).SOMETHING.orElse(Collections.emptyList());

where SOMETHING would be along the lines of:

Arrays.stream(ints).collect(Collectors.toList());

but I can't seem to get the syntax quite right.

This question was helpful but didn't exactly address my issue. Could anyone point me in the right direction? I feel like I'm close...

Thank you very much for your time.

java java-stream

share|improve this question

edited Mar 21 at 3:01

risingTide

asked Mar 21 at 1:31

risingTiderisingTide

62041238

• 
  
  
  

  
  5
  

  
  
  
  
  
  

  
  
  Your original code seems succinct enough
  
  – GBlodgett
  Mar 21 at 1:35
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Fair enough, but I'm curious as to the best way it can be done using streams.
  
  – risingTide
  Mar 21 at 1:36
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  .map(Arrays::asList)
  
  – shmosel
  Mar 21 at 2:05
  

  
  
  
  

add a comment | 

9

1

I'm looking for a succinct way to rewrite a piece of Java code so that it uses streams to convert an array to a list in a null-safe fashion. Here's the original code:

public MailObject toMailObject(final String[] ccAddresses) 
 final MailObject mailObject = new MailObject();

 // line of code to be altered
 mailObject.setCcAddresses(ccAddresses == null 
 ? Collections.emptyList() : Arrays.asList(ccAddresses));

 // other necessary code

 return mailObject;

I've thought of doing something like this:

// psuedocode that obviously doesn't compile
Optional.ofNullable(ccAddresses).SOMETHING.orElse(Collections.emptyList());

where SOMETHING would be along the lines of:

Arrays.stream(ints).collect(Collectors.toList());

but I can't seem to get the syntax quite right.

This question was helpful but didn't exactly address my issue. Could anyone point me in the right direction? I feel like I'm close...

Thank you very much for your time.

java java-stream

share|improve this question

edited Mar 21 at 3:01

risingTide

asked Mar 21 at 1:31

risingTiderisingTide

62041238

• 
  
  
  

  
  5
  

  
  
  
  
  
  

  
  
  Your original code seems succinct enough
  
  – GBlodgett
  Mar 21 at 1:35
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Fair enough, but I'm curious as to the best way it can be done using streams.
  
  – risingTide
  Mar 21 at 1:36
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  .map(Arrays::asList)
  
  – shmosel
  Mar 21 at 2:05
  

  
  
  
  

add a comment | 

I'm looking for a succinct way to rewrite a piece of Java code so that it uses streams to convert an array to a list in a null-safe fashion. Here's the original code:

public MailObject toMailObject(final String[] ccAddresses) 
 final MailObject mailObject = new MailObject();

 // line of code to be altered
 mailObject.setCcAddresses(ccAddresses == null 
 ? Collections.emptyList() : Arrays.asList(ccAddresses));

 // other necessary code

 return mailObject;

I've thought of doing something like this:

// psuedocode that obviously doesn't compile
Optional.ofNullable(ccAddresses).SOMETHING.orElse(Collections.emptyList());

where SOMETHING would be along the lines of:

Arrays.stream(ints).collect(Collectors.toList());

but I can't seem to get the syntax quite right.

This question was helpful but didn't exactly address my issue. Could anyone point me in the right direction? I feel like I'm close...

Thank you very much for your time.

java java-stream

share|improve this question

edited Mar 21 at 3:01

risingTide

asked Mar 21 at 1:31

risingTiderisingTide

62041238

public MailObject toMailObject(final String[] ccAddresses) 
 final MailObject mailObject = new MailObject();

 // line of code to be altered
 mailObject.setCcAddresses(ccAddresses == null 
 ? Collections.emptyList() : Arrays.asList(ccAddresses));

 // other necessary code

 return mailObject;

// psuedocode that obviously doesn't compile
Optional.ofNullable(ccAddresses).SOMETHING.orElse(Collections.emptyList());

Arrays.stream(ints).collect(Collectors.toList());

share|improve this question

edited Mar 21 at 3:01

risingTide

asked Mar 21 at 1:31

risingTiderisingTide

62041238

share|improve this question

edited Mar 21 at 3:01

risingTide

asked Mar 21 at 1:31

risingTiderisingTide

62041238

asked Mar 21 at 1:31

risingTiderisingTide

62041238

asked Mar 21 at 1:31

risingTiderisingTide

62041238

2 Answers
2

active

oldest

votes

6

In my opinion, the code that you have so far is perfectly readable. I think using a Stream for something like this will just complicate things. If you still want to use a Stream, then something like the following would work:

mailObject.setCcAddresses(Stream.ofNullable(ccAddresses)
 .flatMap(Arrays::stream)
 .collect(Collectors.toUnmodifiableList()));

As you can see, this is a more unreadable, and I wouldn't recommend it over your simple ternary expression.

---

Your Optional solution is slightly more readable and would look like the following:

mailObject.setCcAddresses(Optional.ofNullable(ccAddresses)
 .map(Arrays::asList)
 .orElse(Collections.emptyList()));

share|improve this answer

edited Mar 21 at 2:05

answered Mar 21 at 2:00

Jacob G.Jacob G.

16.4k52464

• 
  
  
  

  
  5
  

  
  
  
  
  
  

  
  
  Stream.ofNullable requires Java 9 and Collectors.toUnmodifiableList() even requires Java 10. And when you’re using Java 9 or newer, you can likewise change the original code to mailObject.setCcAddresses(ccAddresses == null? List.of(): List.of(ccAddresses));, whose simplicity will highlight the silliness of using Optional or Stream here even more.
  
  – Holger
  Mar 21 at 9:16
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Good insight onto the Java versions that the first solution uses...and also into the List.of() possibility! Between this and the full answer by @Jacob G. there are a lot of options here; thanks!
  
  – risingTide
  Mar 21 at 18:18
  

  
  
  
  

add a comment | 

9

You might use the map :

List<String> ccAddrs = Optional.ofNullable(ccAddress)
 .map(Arrays::asList)
 .orElse(Collections.emptyList())

share|improve this answer

answered Mar 21 at 2:06

Mạnh Quyết NguyễnMạnh Quyết Nguyễn

11k1930

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I had wondered if the .map() method might be of use; thanks for the full usage in context.
  
  – risingTide
  Mar 21 at 18:23
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @risingTide you're welcome. :D
  
  – Mạnh Quyết Nguyễn
  Mar 22 at 1:48
  

  
  
  
  

add a comment | 

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6

In my opinion, the code that you have so far is perfectly readable. I think using a Stream for something like this will just complicate things. If you still want to use a Stream, then something like the following would work:

mailObject.setCcAddresses(Stream.ofNullable(ccAddresses)
 .flatMap(Arrays::stream)
 .collect(Collectors.toUnmodifiableList()));

As you can see, this is a more unreadable, and I wouldn't recommend it over your simple ternary expression.

---

Your Optional solution is slightly more readable and would look like the following:

mailObject.setCcAddresses(Optional.ofNullable(ccAddresses)
 .map(Arrays::asList)
 .orElse(Collections.emptyList()));

share|improve this answer

edited Mar 21 at 2:05

answered Mar 21 at 2:00

Jacob G.Jacob G.

16.4k52464

• 
  
  
  

  
  5
  

  
  
  
  
  
  

  
  
  Stream.ofNullable requires Java 9 and Collectors.toUnmodifiableList() even requires Java 10. And when you’re using Java 9 or newer, you can likewise change the original code to mailObject.setCcAddresses(ccAddresses == null? List.of(): List.of(ccAddresses));, whose simplicity will highlight the silliness of using Optional or Stream here even more.
  
  – Holger
  Mar 21 at 9:16
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Good insight onto the Java versions that the first solution uses...and also into the List.of() possibility! Between this and the full answer by @Jacob G. there are a lot of options here; thanks!
  
  – risingTide
  Mar 21 at 18:18
  

  
  
  
  

add a comment | 

6

In my opinion, the code that you have so far is perfectly readable. I think using a Stream for something like this will just complicate things. If you still want to use a Stream, then something like the following would work:

mailObject.setCcAddresses(Stream.ofNullable(ccAddresses)
 .flatMap(Arrays::stream)
 .collect(Collectors.toUnmodifiableList()));

As you can see, this is a more unreadable, and I wouldn't recommend it over your simple ternary expression.

---

Your Optional solution is slightly more readable and would look like the following:

mailObject.setCcAddresses(Optional.ofNullable(ccAddresses)
 .map(Arrays::asList)
 .orElse(Collections.emptyList()));

share|improve this answer

edited Mar 21 at 2:05

answered Mar 21 at 2:00

Jacob G.Jacob G.

16.4k52464

• 
  
  
  

  
  5
  

  
  
  
  
  
  

  
  
  Stream.ofNullable requires Java 9 and Collectors.toUnmodifiableList() even requires Java 10. And when you’re using Java 9 or newer, you can likewise change the original code to mailObject.setCcAddresses(ccAddresses == null? List.of(): List.of(ccAddresses));, whose simplicity will highlight the silliness of using Optional or Stream here even more.
  
  – Holger
  Mar 21 at 9:16
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Good insight onto the Java versions that the first solution uses...and also into the List.of() possibility! Between this and the full answer by @Jacob G. there are a lot of options here; thanks!
  
  – risingTide
  Mar 21 at 18:18
  

  
  
  
  

add a comment | 

In my opinion, the code that you have so far is perfectly readable. I think using a Stream for something like this will just complicate things. If you still want to use a Stream, then something like the following would work:

mailObject.setCcAddresses(Stream.ofNullable(ccAddresses)
 .flatMap(Arrays::stream)
 .collect(Collectors.toUnmodifiableList()));

As you can see, this is a more unreadable, and I wouldn't recommend it over your simple ternary expression.

---

Your Optional solution is slightly more readable and would look like the following:

mailObject.setCcAddresses(Optional.ofNullable(ccAddresses)
 .map(Arrays::asList)
 .orElse(Collections.emptyList()));

share|improve this answer

edited Mar 21 at 2:05

answered Mar 21 at 2:00

Jacob G.Jacob G.

16.4k52464

mailObject.setCcAddresses(Stream.ofNullable(ccAddresses)
 .flatMap(Arrays::stream)
 .collect(Collectors.toUnmodifiableList()));

mailObject.setCcAddresses(Optional.ofNullable(ccAddresses)
 .map(Arrays::asList)
 .orElse(Collections.emptyList()));

share|improve this answer

edited Mar 21 at 2:05

answered Mar 21 at 2:00

Jacob G.Jacob G.

16.4k52464

answered Mar 21 at 2:00

Jacob G.Jacob G.

16.4k52464

answered Mar 21 at 2:00

Jacob G.Jacob G.

16.4k52464

9

You might use the map :

List<String> ccAddrs = Optional.ofNullable(ccAddress)
 .map(Arrays::asList)
 .orElse(Collections.emptyList())

share|improve this answer

answered Mar 21 at 2:06

Mạnh Quyết NguyễnMạnh Quyết Nguyễn

11k1930

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I had wondered if the .map() method might be of use; thanks for the full usage in context.
  
  – risingTide
  Mar 21 at 18:23
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @risingTide you're welcome. :D
  
  – Mạnh Quyết Nguyễn
  Mar 22 at 1:48
  

  
  
  
  

add a comment | 

9

You might use the map :

List<String> ccAddrs = Optional.ofNullable(ccAddress)
 .map(Arrays::asList)
 .orElse(Collections.emptyList())

share|improve this answer

answered Mar 21 at 2:06

Mạnh Quyết NguyễnMạnh Quyết Nguyễn

11k1930

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I had wondered if the .map() method might be of use; thanks for the full usage in context.
  
  – risingTide
  Mar 21 at 18:23
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @risingTide you're welcome. :D
  
  – Mạnh Quyết Nguyễn
  Mar 22 at 1:48
  

  
  
  
  

add a comment | 

You might use the map :

List<String> ccAddrs = Optional.ofNullable(ccAddress)
 .map(Arrays::asList)
 .orElse(Collections.emptyList())

share|improve this answer

answered Mar 21 at 2:06

Mạnh Quyết NguyễnMạnh Quyết Nguyễn

11k1930

List<String> ccAddrs = Optional.ofNullable(ccAddress)
 .map(Arrays::asList)
 .orElse(Collections.emptyList())

share|improve this answer

answered Mar 21 at 2:06

Mạnh Quyết NguyễnMạnh Quyết Nguyễn

11k1930

answered Mar 21 at 2:06

Mạnh Quyết NguyễnMạnh Quyết Nguyễn

11k1930

answered Mar 21 at 2:06

Mạnh Quyết NguyễnMạnh Quyết Nguyễn

11k1930