How can I join a Java List into a single String?

General Discussions
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1

JavaScript has Array.join(), which allows joining elements like this:

["Bill","Bob","Steve"].join(" and ") 
// Output: "Bill and Bob and Steve"

Does Java have a built-in way to achieve this, or do I need to manually implement a java list join method using StringBuilder?

2

I’ve been working with Java for a few years now, and when Java 8 introduced String.join(), it honestly made life so much easier for simple cases.

If you’re using Java 8 or later, you’re all set! Java has a built-in way to handle a java list join neatly.

import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<String> names = List.of("Bill", "Bob", "Steve");
        String result = String.join(" and ", names);
        System.out.println(result); // Output: Bill and Bob and Steve
    }
}

:white_check_mark: Why choose this?

  • It’s super clean and easy to read.
  • No need for any manual loops or condition checks.
  • Perfect when you just need to quickly stitch together a list of strings.

If you have a List<String>, this is definitely the fastest and simplest java list join method to reach for.

3

Over time, I’ve noticed that sometimes you need a bit more flexibility — and that’s where Java Streams really shine.

If you’re already working with streams or need more control, Collectors.joining() is a fantastic tool for your java list join needs.

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

public class Main {
    public static void main(String[] args) {
        List<String> names = List.of("Bill", "Bob", "Steve");
        String result = names.stream().collect(Collectors.joining(" and "));
        System.out.println(result); // Output: Bill and Bob and Steve
    }
}

:white_check_mark: Why go for this?

  • Fits perfectly if you’re already using Streams elsewhere.
  • Lets you easily add a prefix, suffix, or even manage empty lists.

Example with extra formatting:

String result = names.stream().collect(Collectors.joining(" and ", "[", "]"));
System.out.println(result); // Output: [Bill and Bob and Steve]

When you need that little extra polish or customization in your java list join, Streams are definitely the way to go.

4

Having worked on a few large-scale data processing projects, I’ve learned that sometimes you just can’t beat old-school efficiency.

If you’re handling very large lists where performance is critical, manual construction using StringBuilder is still the most efficient java list join technique.

import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<String> names = List.of("Bill", "Bob", "Steve");
        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < names.size(); i++) {
            sb.append(names.get(i));
            if (i < names.size() - 1) {
                sb.append(" and ");
            }
        }

        System.out.println(sb.toString()); // Output: Bill and Bob and Steve
    }
}

:white_check_mark: Why consider this?

  • Gives you complete control over how the string is built.
  • Highly efficient for very large datasets where even minor optimizations matter.
  • Avoids creating unnecessary intermediate strings.

That being said, for everyday cases, String.join() or Collectors.joining() should cover most of your java list join scenarios beautifully — but it’s always good to know when to go the manual route!