The Simplest Way to Comma-Delimit a List

The simplest way to comma-delimit a list?

Java 8 and later

Using StringJoiner class, and forEach method :

StringJoiner joiner = new StringJoiner(",");
list.forEach(item -> joiner.add(item.toString());
return joiner.toString();

Using Stream, and Collectors:

return list.stream().
       map(Object::toString).
       collect(Collectors.joining(",")).toString();

Java 7 and earlier

See also #285523

String delim = "";
for (Item i : list) {
    sb.append(delim).append(i);
    delim = ",";
}

Best way to convert list to comma separated string in java

Since Java 8:

String.join(",", slist);

From Apache Commons library:

import org.apache.commons.lang3.StringUtils

Use:

StringUtils.join(slist, ',');

Another similar question and answer here

Convert a list of string into a comma separated string without duplications

The best to avoid duplicates is to use a Set

• TreeSet for alphabetical order

• LinkedHashSet to keep insertion order (initial order)

StringBuilder result = new StringBuilder();
String delimiter= "";
for (String i : new LinkedHashSet<String>(list)) {
    result.append(delimiter).append(i);
    delimiter = ",";
}
return result.toString();

But you can just do String.join(',', new LinkedHashSet<String>(list))

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Back to List

List<String> inputList = (unique) ? new ArrayList<>(new HashSet<>(list)) : list;

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Case-insensitive

Set<String> check = new HashSet<String>();
StringBuilder result = new StringBuilder();
String delimiter= "";
for (String i : list) {
    if(!check.contains(i.toLowerCase())){
        result.append(delimiter).append(i);
        delimiter = ",";
        check.add(i.toLowerCase());
    }
}
return result.toString();

Convert a list of integers into a comma-separated string

Yes. However, there is no Collectors.joining for a Stream<Integer>; you need a Stream<String> so you should map before collecting. Something like,

System.out.println(i.stream().map(String::valueOf)
        .collect(Collectors.joining(",")));

Which outputs

1,2,3,4,5

Also, you could generate Stream<Integer> in a number of ways.

System.out.println(
        IntStream.range(1, 6).boxed().map(String::valueOf)
               .collect(Collectors.joining(","))
);

How would you make a comma-separated string from a list of strings?

my_list = ['a', 'b', 'c', 'd']
my_string = ','.join(my_list)

'a,b,c,d'

This won't work if the list contains integers

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And if the list contains non-string types (such as integers, floats, bools, None) then do:

my_string = ','.join(map(str, my_list)) 

Creating a comma separated list from IListstring or IEnumerablestring

.NET 4+

IList<string> strings = new List<string>{"1","2","testing"};
string joined = string.Join(",", strings);

Detail & Pre .Net 4.0 Solutions

IEnumerable<string> can be converted into a string array very easily with LINQ (.NET 3.5):

IEnumerable<string> strings = ...;
string[] array = strings.ToArray();

It's easy enough to write the equivalent helper method if you need to:

public static T[] ToArray(IEnumerable<T> source)
{
    return new List<T>(source).ToArray();
}

Then call it like this:

IEnumerable<string> strings = ...;
string[] array = Helpers.ToArray(strings);

You can then call string.Join. Of course, you don't have to use a helper method:

// C# 3 and .NET 3.5 way:
string joined = string.Join(",", strings.ToArray());
// C# 2 and .NET 2.0 way:
string joined = string.Join(",", new List<string>(strings).ToArray());

The latter is a bit of a mouthful though :)

This is likely to be the simplest way to do it, and quite performant as well - there are other questions about exactly what the performance is like, including (but not limited to) this one.

As of .NET 4.0, there are more overloads available in string.Join, so you can actually just write:

string joined = string.Join(",", strings);

Much simpler :)

Easiest way to convert list to a comma separated string by a Specific Property?

This is very easy , Isn't it ?

string sCategories = string.Join(",", categories.Select(x => x.Name));

Easy way to turn JavaScript array into comma-separated list?

The Array.prototype.join() method:

var arr = ["Zero", "One", "Two"];
document.write(arr.join(", "));

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