StringJoiner merge() method in Java

Difficulty Level : Basic
Last Updated : 12 Sep, 2018

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 program to demonstrate
// merge() method of StringJoiner
  
import java.util.StringJoiner;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // Creating StringJoiner with delimeter " "
        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 delimeter “, ”

// Java program to demonstrate
// merge() method of StringJoiner
  
import java.util.StringJoiner;
  
public class GFG1 {
    public static void main(String[] args)
    {
  
        // Creating StringJoiner with delimeter ", "
        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 program to demonstrate
// merge() method of StringJoiner
  
import java.util.StringJoiner;
  
public class GFG1 {
    public static void main(String[] args)
    {
  
        // Creating StringJoiner with delimeter ", "
        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

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