Java String join() Method With Examples

In Java 8 join() method has been added to the Java String class that joins together the given strings using the specified delimiter.

Java String join() method

There are two variants of the join() method-

public static String join(CharSequence delimiter, CharSequence... elements)- This method returns a new String created by joining together the elements using the specified delimiter.
public static String join(CharSequence delimiter, Iterable<? extends CharSequence> elements)- Here elements is an Iterable that will have its elements joined together and delimiter is a sequence of characters that is used to separate each of the elements in the resulting String.

Java String join() method examples

1. Joining 3 strings using space (" ") as delimiter and using colon ":" as delimiter.

public class JoinStrings {
  public static void main(String[] args) {
    String str1 = "Java";
    String str2 = "Python";
    String str3 = "Scala";

    // joining using space as delimiter
    String joinedStr = String.join(" ", str1, str2, str3);
    System.out.println("Joined String- " + joinedStr);
    // joining using colon as delimiter
    joinedStr = String.join(":", str1, str2, str3);
    System.out.println("Joined String- " + joinedStr);
  }
}

Output

Joined String- Java Python Scala
Joined String- Java:Python:Scala

2- Joining List elements using join() method. Using the second variant of join method where an iterable is passed as parameter we can join List elements (or Set).

import java.util.Arrays;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

public class JoinStrings {
  public static void main(String[] args) {
    List<String> list = Arrays.asList("Java", "Python", "Scala");

    // joining list elements using colon as delimiter
    String joinedStr = String.join(":", list);
    System.out.println("Joined String- " + joinedStr);
    
    // joining set elements using pipe as delimiter
    Set<String> strings = new LinkedHashSet<>(list);
    joinedStr = String.join("|", strings);
    System.out.println("Joined String- " + joinedStr);
  }
}

Output

Joined String- Java:Python:Scala
Joined String- Java|Python|Scala

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