Java String join()

In this tutorial, we will learn about the Java String join() method with the help of examples.

The join() method returns a new string with the given elements joined with the specified delimiter.

Example

class Main {
  public static void main(String[] args) {
    String str1 = "I";
    String str2 = "love";
    String str3 = "Java";

    // join strings with space between them
    String joinedStr = String.join(" ", str1, str2, str3);

    System.out.println(joinedStr);
  }
}

// Output: I love Java

Syntax of join()

The syntax of the string join() method is either:

String.join(CharSequence delimiter, 
            Iterable elements)

String.join(CharSequence delimiter, 
            CharSequence... elements)

Here, ... signifies there can be one or more CharSequence.

Note: join() is a static method. You do not need to create a string object to call this method. Rather, we call the method using the class name String.

join() Parameters

The join() method takes two parameters.

delimiter - the delimiter to be joined with the elements
elements - elements to be joined

Notes:

You can pass any class that implements CharSequence to join().
If an iterable is passed, its elements will be joined. The iterable must implement CharSequence.
String, StringBuffer, CharBuffer etc. are CharSequence as these classes implement it.

join() Return Value

returns a string

Example 1: Java String join() With CharSequence()

class Main {
  public static void main(String[] args) {
    String result;

    result = String.join("-", "Java", "is", "fun");

    System.out.println(result);  // Java-is-fun

  }
}

Here, we have passed three strings Java, is and fun to the join() method. These strings are joined using the - delimiter.

Example 2: Java String join() With Iterable

import java.util.ArrayList;

class Main {
  public static void main(String[] args) {
    ArrayList<String> text = new ArrayList<>();

    // adding elements to the arraylist
    text.add("Java");
    text.add("is");
    text.add("fun");

    String result;

    result = String.join("-", text);

    System.out.println(result);  // Java-is-fun

  }
}

Here, an ArrayList of String type is created. The elements of array list are joined using the - delimiter.