Convert List to Comma Separated String in Java

All of the below methods produce the same result of joining the elements of the List into a single String with space as a delimiter.

Using Collectors.joining:

In Java, you can use the Collectors.joining() method to join the elements of a List into a single String. Here’s an example:

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class ListToStringExample {
    public static void main(String[] args) {
        List<String> list = Arrays.asList("Hello", "world", "!", "How", "are", "you", "?");

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

        System.out.println(result); 
    }
}

Using String.join()

import java.util.Arrays;
import java.util.List;

public class ListToStringExample {
    public static void main(String[] args) {
        List<String> list = Arrays.asList("Hello", "world", "!", "How", "are", "you", "?");

        String result = String.join(",", list);

        System.out.println(result); // Output: Hello,world, !, How, are, you, ?
    }
}

Using a StringBuilder

import java.util.Arrays;
import java.util.List;

public class ListToStringExample {
    public static void main(String[] args) {
        List<String> list = Arrays.asList("Hello", "world", "!", "How", "are", "you", "?");

        StringBuilder sb = new StringBuilder();
        for (String s : list) {
            sb.append(s).append(",");
        }
        String result = sb.toString().trim();

        System.out.println(result); // Output: Hello world ! How are you ?
    }
}