Convert a List to Comma-Separated String in Java

This post will discuss how to convert a List to a comma-separated String in Java.

1. Using Apache Commons Lang

Apache Commons Lang library offers the StringUtils.join() method, which can concatenate elements of an iterable together using the specified separator.

import org.apache.commons.lang3.StringUtils;

import java.util.Arrays;

import java.util.List;

class Main

{

public static void main(String[] args)

{

List<String> words = Arrays.asList("Hello", "World");

String str = StringUtils.join(words, ',');

System.out.println(str);

}

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Output:

Hello,World

2. Using Guava

Similar to Apache Commons Lang, the Guava library offers a Joiner class to join elements of an iterable using a separator between consecutive elements.

import com.google.common.base.Joiner;

import java.util.Arrays;

import java.util.List;

class Main

{

public static void main(String[] args)

{

List<String> words = Arrays.asList("Hello", "World");

String str = Joiner.on(',').join(words);

System.out.println(str);

}

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Output:

Hello,World

3. Using `String.join()` method

Since Java 8, you can use the String.join() method that works only for Iterable<String>. It joins strings together with a specified separator.

import java.util.Arrays;

import java.util.List;

class Main

{

public static void main(String[] args)

{

List<String> words = Arrays.asList("Hello", "World");

String str = String.join(",", words);

System.out.println(str);

}

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Output:

Hello,World

4. Stream API

From Java 8 onwards, this can be efficiently done using joining Collector:

import java.util.Arrays;

import java.util.List;

import java.util.stream.Collectors;

class Main

{

public static void main(String[] args)

{

List<String> words = Arrays.asList("Hello", "World");

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

System.out.println(str);

}

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Output:

Hello,World

5. Using `StringBuilder`

Finally, you can iterate through the list and append each value to a StringBuilder along with the specified delimiter. The following solution demonstrates this by creating a utility function that returns the string representation of the StringBuilder.

import java.util.Arrays;

import java.util.List;

class Main

{

public static<T> String join(List<T> list) {

StringBuilder sb = new StringBuilder();

String sep = "";

for (T e : list) {

sb.append(sep).append(e);

sep = ",";

}

return sb.toString();

}

public static void main(String[] args)

{

List<String> words = Arrays.asList("Hello", "World");

String str = join(words);

System.out.println(str);

}

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Output:

Hello,World

That’s all about converting a List to a comma-separated String in Java.

Convert a List to Comma-Separated String in Java

1. Using Apache Commons Lang

2. Using Guava

3. Using String.join() method

4. Stream API

5. Using StringBuilder

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3. Using `String.join()` method

5. Using `StringBuilder`