Get empty string when null

Question

I want to get string values of my fields (they can be type of long string or any object),

if a field is null then it should return empty string, I did this with guava;

nullToEmpty(String.valueOf(gearBox))
nullToEmpty(String.valueOf(id))
...

But this returns null if gearbox is null! Not empty string because valueOf methdod returns string "null" which leads to errors.

Any Ideas?

EDIt: there are 100s fields I look for something easy to implement

arshajii · Accepted Answer · 2014-02-21T14:08:22.353

247

You can use Objects.toString() (standard in Java 7):

Objects.toString(gearBox, "")

Objects.toString(id, "")

From the linked documentation:

public static String toString(Object o, String nullDefault)

Returns the result of calling toString on the first argument if the first argument is not null and returns the second argument otherwise.

Parameters:
o - an object
nullDefault - string to return if the first argument is null

Returns:
the result of calling toString on the first argument if it is not null and the second argument otherwise.

See Also:
toString(Object)

edited Feb 21 '14 at 14:08

answered Feb 21 '14 at 14:02

arshajii

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@Spring You should consider upgrading, especially with Java 8 coming out soon. In any case, I'll leave this answer in case it can be helpful for future visitors. – arshajii Feb 21 '14 at 14:09
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Downvoter: please leave a comment. I would like to know what is wrong with my answer, and a downvote alone doesn't tell me. – arshajii Feb 21 '14 at 14:21
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NIce. I suggest `Objects.toString(id, "").trim()` – Wender Oct 21 '17 at 18:26
why it requires > API 19... its a simple check. i guess i have to write that my self – M.kazem Akhgary Nov 01 '18 at 09:58
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The risk is that u r losing the type of your string. It is currently a String but if it will change to a different type in the future he compiler won't protect u – ozma Jul 29 '19 at 06:32

score 68 · Answer 2 · answered Mar 20 '17 at 22:17

68

For java 8 you can use Optional approach:

Optional.ofNullable(gearBox).orElse("");
Optional.ofNullable(id).orElse("");

answered Mar 20 '17 at 22:17

Federico Piazza

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if id is not a string, it seems that the second line code cannot work – jack jin Nov 18 '19 at 07:23
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This does two method calls and allocates a new object and immediately discards it. This is not an improvement over the simple `gearBox == null ? "" : gearBox`. A single method call like `StringUtils.defaultString` is more JIT friendly. – Vroo Jul 21 '20 at 01:56
@Vroo if you don't want the discard then the `orElseGet` can be use instead – Federico Piazza Jul 21 '20 at 02:11
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@FedericoPiazza That's not an improvement. First, `orElseGet` takes a delegate so now I have ***three*** method calls. Second, an `Optional` object still gets created and then discarded. – Vroo Jul 22 '20 at 03:12

Keppil · Answer 3 · 2014-02-21T14:10:29.397

37

If you don't mind using Apache commons, they have a StringUtils.defaultString(String str) that does this.

Returns either the passed in String, or if the String is null, an empty String ("").

If you also want to get rid of "null", you can do:

StringUtils.defaultString(str).replaceAll("^null$", "")

or to ignore case:

StringUtils.defaultString(str).replaceAll("^(?i)null$", "")

edited Feb 21 '14 at 14:10

answered Feb 21 '14 at 14:02

Keppil

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what if string is string "null"? thats my problem – Spring Feb 21 '14 at 14:04
@Spring: Updated to take care of that case too. – Keppil Feb 21 '14 at 14:11
`StringUtils.defaultString` already checks for null. So the `replaceAll` is only changes the string is when it's a literal `"null"`, which is not what was asked for. Here's the source: `public static String defaultString(String str) { return str == null ? "" : str; }` – Vroo Jul 21 '20 at 02:00
I believe the first comment concerned the literal string `"null"` – Keppil Aug 04 '20 at 08:56

score 23 · Answer 4 · edited May 03 '18 at 06:41

23

If alternative way, Guava provides Strings.nullToEmpty(String).

Source code

String str = null;
str = Strings.nullToEmpty(str);
System.out.println("String length : " + str.length());

Result

edited May 03 '18 at 06:41

coder

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answered May 03 '18 at 06:06

Won-Sik Kim

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score 10 · Answer 5 · answered Feb 21 '14 at 14:00

10

Use an inline null check

gearBox == null ? "" : String.valueOf(gearBox);

answered Feb 21 '14 at 14:00

Samhain

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Two seconds too fast! – Rainbolt Feb 21 '14 at 14:01
@Samhain there are 100s fields I look for something easy to implkement – Spring Feb 21 '14 at 14:01

score 10 · Answer 6 · answered Jan 29 '21 at 12:49

StringUtils.defaultString(String str) Returns either the passed in String, or if the String is null, an empty String ("").

Example from java doc

StringUtils.defaultString(null) will return "" StringUtils.defaultString("") will return "" StringUtils.defaultString("bat") will return "bat"

score 6 · Answer 7 · answered Feb 21 '14 at 14:20

6

Since you're using guava:

Objects.firstNonNull(gearBox, "").toString();

answered Feb 21 '14 at 14:20

renke

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Is that you in your profile picture? Isn't that Jon? – Kai Feb 21 '14 at 14:22
from guava 18 you need to use `MoreObjects.firstNonNull` – Juan Rada Dec 13 '17 at 13:50

score 3 · Answer 8 · answered Aug 25 '20 at 22:49

3

In Java 9+ use : Objects.requireNonNullElse (obj, defaultObj) https://docs.oracle.com/javase/9/docs/api/java/util/Objects.html#requireNonNullElse-T-T-

//-- returns empty string if obj is null
Objects.requireNonNullElse (obj, "")

answered Aug 25 '20 at 22:49

Ari Singh

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score 0 · Answer 9 · answered Aug 22 '23 at 13:19

0

This should do the trick: "" + gearBox

answered Aug 22 '23 at 13:19

Flavian-Calinic Stuparu

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Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Community Aug 24 '23 at 09:25

Get empty string when null

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