StringJoiner setEmptyValue() method in Java

The setEmptyValue(CharSequence emptyValue) of StringJoiner sets the sequence of characters to be used when determining the string representation of this StringJoiner and no elements have been added yet, that is, when it is empty. A copy of the emptyValue parameter is made for this purpose. Note that once an add method has been called, the StringJoiner is no longer considered empty, even if the element(s) added correspond to the empty String. Syntax:

public StringJoiner setEmptyValue(CharSequence emptyValue)

Parameters: This method accepts a mandatory parameter emptyValue which is the characters to return as the value of an empty StringJoiner Returns: This method returns this StringJoiner itself, so the calls may be chained Exception: This method throws NullPointerException when the emptyValue parameter is null Below examples illustrates the setEmptyValue() method: Example 1:

Java

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

import java.util.StringJoiner;

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

        // Create a StringJoiner
        StringJoiner str = new StringJoiner(" ");

        // Print the empty StringJoiner
        System.out.println("Initial StringJoiner: "
                           + str);

        // Add an emptyValue
        // using setEmptyValue() method
        str.setEmptyValue("StringJoiner is empty");

        // Print the StringJoiner
        System.out.println("After setEmptyValue(): "
                           + str);

        // Add elements to StringJoiner
        str.add("Geeks");
        str.add("forGeeks");

        // Print the StringJoiner
        System.out.println("Final StringJoiner: "
                           + str);
    }
}

Output:

Initial StringJoiner: 
After setEmptyValue(): StrigJoiner is empty
Final StringJoiner: Geeks forGeeks

Example 2: To demonstrate NullPointerException 

Java

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

import java.util.StringJoiner;

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

        // Create a StringJoiner
        StringJoiner str = new StringJoiner(" ");

        // Print the empty StringJoiner
        System.out.println("Initial StringJoiner: "
                           + str);

        try {
            // Add a null emptyValue
            // using setEmptyValue() method
            str.setEmptyValue(null);
        }
        catch (Exception e) {
            System.out.println("Exception when adding null"
                               + " in setEmptyValue(): " + e);
        }
    }
}

Output:

Initial StringJoiner: 
Exception when adding null in setEmptyValue(): 
    java.lang.NullPointerException: 
    The empty value must not be null

Time complexity: O(1).

Auxiliary Space: O(1).