In this short article, we will discuss four approaches to join multiple strings in Java.

Approach 1 - Using StringBuilder
Approach 2 - Using Java 8 Stream APIs
Approach 3 - Using Java 8 StringJoiner
Approach 4 - Using String.join() method

Join Multiple Strings in Java using Delimiter (Java 8)

package com.java.tutorials.programs;

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

/**
 * Join Multiple Strings in Java using Delimiter
 * @author Ramesh Fadatare
 *
 */
public class Java8Program {

    public static void main(String[] args) {

        String[] strArray = {
            "Banana",
            "Mango",
            "Apple",
            "Watermelon",
            "Grapes"
        };
        String delimiter = "|";

        // Approach 1

        StringBuilder result = new StringBuilder();

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

        result.append(strArray[i]);
        System.out.println(" Approach 1 Output => " + result.toString());

        // Approach 2
        String output = Arrays.stream(strArray, 0, strArray.length)
            .collect(Collectors.joining(String.valueOf(delimiter)));

        System.out.println(" Approach 2 Output => " + output);

        // Approach 3
        StringJoiner joiner = new StringJoiner(String.valueOf(delimiter));

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

        System.out.println(" Approach 3 Output => " + joiner.toString());

        // Approach 4 
        String output1 = String.join(delimiter, strArray);
        System.out.println(" Approach 4 Output => " + output1);
    }
}

Output:

 Approach 1 Output => Banana|Mango|Apple|Watermelon|Grapes
 Approach 2 Output => Banana|Mango|Apple|Watermelon|Grapes
 Approach 3 Output => Banana|Mango|Apple|Watermelon|Grapes
 Approach 4 Output => Banana|Mango|Apple|Watermelon|Grapes