Convert Java Set to Java Comma Separated String

Question

I have a java Set

private Set<String> packageCategories;

This has the value ['Abc','Def']. I want to display the value of packageCategories in the UI which now displays as ['Abc','Def'] but I want to display it as simply 'Abc', 'Def.

I tried

String.join(",", packageCategories);
context.put("packageCategories", packageCategories);

I am getting compilation error

 incompatible types: java.util.Set<java.lang.String> cannot be converted to java.lang.String.

How can I achieve this? I searched in StackOverflow and it has answers to convert List to comma separated string. But I didn't find any answer to convert Set to comma separated string.

The answer given in Fastest way to put contents of Set<String> to a single String with words separated by a whitespace? does not work for me.

PS: I am not a JAVA Developer.

Please show the full code ([mcve]). The code you show is not responsible for the error, as it will work fine since `Set` is of type `Iterable extends CharSequence>` (see [documentation](https://docs.oracle.com/javase/10/docs/api/java/lang/String.html#join(java.lang.CharSequence,java.lang.Iterable))). — Zabuzard, Dec 07 '18 at 09:03
Please share the code where you are performing the display. It looks like you are printing out the collection instead of each item. You will need a loop for that. — , Dec 07 '18 at 09:07

Nicholas K · Accepted Answer · 2018-12-07T09:06:13.580

5

You can achieve the same using streams :

String collect = packageCategories.stream().collect(Collectors.joining(","));

With your original code snippet you can use :

String.join(",", packageCategories).replaceAll("[\\[\\]]", "")

edited Dec 07 '18 at 09:06

answered Dec 07 '18 at 09:01

Nicholas K

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It works with `Set` as well. The code OP showed is not responsible for the error. – Zabuzard Dec 07 '18 at 09:02
I get [6496,89] cannot find symbol [exec] [ERROR] symbol: variable Collectors [exec] [ERROR] location: class com.collabnet.ctf.monitoring.MonitoringHelperBean [exec] [ERROR] -> [Help 1] for using Collectors. – Suganya Selvarajan Dec 07 '18 at 09:23
Which version of java are you working on? Both solutions will work only on java 1.8 and higher. – Nicholas K Dec 07 '18 at 09:23
import java.util.stream.Collectors with your answer works. Please add this also in your answer. Would be helpful for newbies – Suganya Selvarajan Dec 07 '18 at 09:34
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If you were working on an IDE the auto-import would fetch that for you :) – Nicholas K Dec 07 '18 at 09:37

score 5 · Answer 2 · answered Dec 07 '18 at 09:04

5

You need to use StringUtils not String

    StringUtils.join(packageCategories,",")

answered Dec 07 '18 at 09:04

Monis Majeed

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This is a workable solution. Thanks – Md. Sajedul Karim Aug 01 '22 at 09:00

Convert Java Set to Java Comma Separated String

2 Answers2