Join multiple strings with a delimiter in Java

 Write a program that joins the given strings by the given delimiter.

We will show four ways to join the given strings by the given delimiter n Java:

1. Join multiple strings via Java 8, String.join()
2. Join multiple strings via StringBuilder
3. Join multiple strings via Java 8, Collectors.joining()
4. Join multiple strings via Java 8, StringJoiner

Java program to Join multiple strings with a delimiter in Java

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

public final class Strings {

    public static String joinByDelimiterV1(char delimiter, String... args) {

        if (args == null || args.length == 0) {
            // or throw IllegalArgumentException
            return "";
        }

        StringBuilder result = new StringBuilder();

        int i = 0;
        for (i = 0; i < args.length - 1; i++) {
            result.append(args[i]).append(delimiter);
        }

        result.append(args[i]);

        return result.toString();
    }

    public static String joinByDelimiterV2(char delimiter, String... args) {

        if (args == null || args.length == 0) {
            // or throw IllegalArgumentException
            return "";
        }

        return Arrays.stream(args, 0, args.length)
                .collect(Collectors.joining(String.valueOf(delimiter)));
    }

    public static String joinByDelimiterV3(char delimiter, String... args) {
        
        if (args == null || args.length == 0) {
            // or throw IllegalArgumentException
            return "";
        }

        StringJoiner joiner = new StringJoiner(String.valueOf(delimiter));

        for (String arg : args) {
            joiner.add(arg);
        }

        return joiner.toString();
    }
}

Test

public class Main {

    private static final String TEXT_1 = "Illinois";
    private static final String TEXT_2 = "Mathematics";
    private static final String TEXT_3 = "and";
    private static final String TEXT_4 = "Science";
    private static final String TEXT_5 = "Academy";

    public static void main(String[] args) {

        System.out.println("Join multiple string via Java 8, String.join():");

        String stringV1 = String.join(" ", TEXT_1, TEXT_2, TEXT_3, TEXT_4, TEXT_5);

        System.out.println("String: " + stringV1);

        System.out.println();
        System.out.println("Join multiple string via StringBuilder:");
        String stringV2 = Strings.joinByDelimiterV1(' ', TEXT_1, TEXT_2, TEXT_3, TEXT_4, TEXT_5);
        System.out.println("String: " + stringV2);

        System.out.println();
        System.out.println("Join multiple string via Java 8, Collectors.joining():");
        String stringV3 = Strings.joinByDelimiterV2(' ', TEXT_1, TEXT_2, TEXT_3, TEXT_4, TEXT_5);
        System.out.println("String: " + stringV3);

        System.out.println();
        System.out.println("Join multiple string via Java 8, StringJoiner:");
        String stringV4 = Strings.joinByDelimiterV3(' ', TEXT_1, TEXT_2, TEXT_3, TEXT_4, TEXT_5);
        System.out.println("String: " + stringV4);
    }
}

Output:

Join multiple string via Java 8, String.join():
String: Illinois Mathematics and Science Academy

Join multiple string via StringBuilder:
String: Illinois Mathematics and Science Academy

Join multiple string via Java 8, Collectors.joining():
String: Illinois Mathematics and Science Academy

Join multiple string via Java 8, StringJoiner:
String: Illinois Mathematics and Science Academy