StringJoiner merge() method in Java

The merge(StringJoiner other) of StringJoiner adds the contents of the given StringJoiner without prefix and suffix as the next element if it is non-empty. If the given StringJoiner is empty, the call has no effect.
Syntax:

public StringJoiner merge(StringJoiner other)

Parameters: This method accepts a mandatory parameter other which is the StringJoiner whose contents should be merged into this one
Returns: This method returns this StringJoiner
Exception: This method throws NullPointerException if the other StringJoiner is null
Below programs illustrate the merge() method:
Example 1: To demonstrate merge() with delimiter ” “

Java

// Java program to demonstrate
// merge() method of StringJoiner

import java.util.StringJoiner;

public class GFG {
    public static void main(String[] args)
    {

        // Creating StringJoiner with delimiter " "
        StringJoiner str1 = new StringJoiner(" ");

        // Adding elements in the StringJoiner
        str1.add("Geeks");
        str1.add("for");
        str1.add("Geeks");

        // Print the StringJoiner
        System.out.println("StringJoiner 1: "
                           + str1.toString());

        // Creating the second StringJoiner
        StringJoiner str2 = new StringJoiner(" ");

        str2.add("A");
        str2.add("Computer");
        str2.add("Portal");

        // Print the second StringJoiner
        System.out.println("StringJoiner 2: "
                           + str2.toString());

        // Merging the StringJoiner using merge()
        StringJoiner str = str1.merge(str2);

        // Printing the merged StringJoiner
        System.out.println("Merged StringJoiner : "
                           + str);
    }
}

Output:

StringJoiner 1: Geeks for Geeks
StringJoiner 2: A Computer Portal
Merged StringJoiner : Geeks for Geeks A Computer Portal

Example 2: To demonstrate merge() with delimiter “, “

Java

// Java program to demonstrate
// merge() method of StringJoiner

import java.util.StringJoiner;

public class GFG1 {
    public static void main(String[] args)
    {

        // Creating StringJoiner with delimiter ", "
        StringJoiner str1 = new StringJoiner(", ");

        // Adding elements in the StringJoiner
        str1.add("Geeks");
        str1.add("for");
        str1.add("Geeks");

        // Print the StringJoiner
        System.out.println("StringJoiner 1: "
                           + str1.toString());

        // Creating the second StringJoiner
        StringJoiner str2 = new StringJoiner(", ");

        str2.add("A");
        str2.add("Computer");
        str2.add("Portal");

        // Print the StringJoiner
        System.out.println("StringJoiner 2: "
                           + str2.toString());

        // Merging the StringJoiner using merge()
        StringJoiner str = str1.merge(str2);

        // Printing the merged StringJoiner
        System.out.println("Merged StringJoiner : "
                           + str);
    }
}

Output:

StringJoiner 1: Geeks, for, Geeks
StringJoiner 2: A, Computer, Portal
Merged StringJoiner : Geeks, for, Geeks, A, Computer, Portal

Example 3: To demonstrate NullPointerException

Java

// Java program to demonstrate
// merge() method of StringJoiner

import java.util.StringJoiner;

public class GFG1 {
    public static void main(String[] args)
    {

        // Creating StringJoiner with delimiter ", "
        StringJoiner str1 = new StringJoiner(", ");

        // Adding elements in the StringJoiner
        str1.add("Geeks");
        str1.add("for");
        str1.add("Geeks");

        // Print the StringJoiner
        System.out.println("StringJoiner 1: "
                           + str1.toString());

        // Creating the second StringJoiner
        // to be merged as null
        StringJoiner str2 = null;

        // Print the StringJoiner
        System.out.println("StringJoiner 2: "
                           + str2);

        try {

            // Merging the StringJoiner using merge()
            StringJoiner str = str1.merge(str2);
        }
        catch (Exception e) {
            System.out.println("Exception during merge: "
                               + e);
        }
    }
}

Output:

StringJoiner 1: Geeks, for, Geeks
StringJoiner 2: null
Exception during merge: java.lang.NullPointerException