MessageFormat formatToCharacterIterator() method in Java with Example

The formatToCharacterIterator() method of java.text.MessageFormat class is used to format an array of object and insert them into the pattern of message format object.
Syntax:

public AttributedCharacterIterator formatToCharacterIterator(Object arguments)

Parameter: This method takes array of object as an parameter over which formatting is going to take place.
Return Value: This method returns attribute character iterator which will describe the formatted value .
Exception: This method throws NullPointerException if argument is null.
Below are the examples to illustrate the formatToCharacterIterator() method:
Example 1:

Java

// Java program to demonstrate
// formatToCharacterIterator() method

import java.text.*;
import java.util.*;
import java.io.*;

public class GFG {
    public static void main(String[] argv)
    {
        try {
            // creating and initializing new MessageFormat Object
            MessageFormat mf
                = new MessageFormat("{0, number, #}, {0, number, #.##}, {0, number}");

            // Creating and initializing an array of type Double
            // to be formatted
            Object[] objs = { new Double(4.234567) };

            // Formatting an array of object
            // using formatToCharacterIterator() method
            CharacterIterator str = mf.formatToCharacterIterator(objs);

            // display the result
            System.out.print("formatted array : ");
            System.out.print(str.first());
            for (int i = 0; i <= str.getEndIndex() - 2; i++)
                System.out.print(str.next());
        }
        catch (NullPointerException e) {
            System.out.println("pattern is null ");
            System.out.println("Exception thrown : " + e);
        }
    }
}

Output:

formatted array : 4, 4.23, 4.235

Example 2:

Java

// Java program to demonstrate
// formatToCharacterIterator() method

import java.text.*;
import java.util.*;
import java.io.*;

public class GFG {
    public static void main(String[] argv)
    {
        try {
            // creating and initializing new MessageFormat Object
            MessageFormat mf
                = new MessageFormat("{0, number, #}, {0, number, #.##}, {0, number}");

            // Creating and initializing an array of type Double
            // to be formatted
            Object[] objs = { new Double(4.234567) };

            // Formatting an array of object
            // using formatToCharacterIterator() method
            CharacterIterator str = mf.formatToCharacterIterator(null);

            // display the result
            System.out.print("formatted array : ");
            System.out.print(str.first());
            for (int i = 0; i <= str.getEndIndex() - 2; i++)
                System.out.print(str.next());
        }
        catch (NullPointerException e) {
            System.out.println("argument is null ");
            System.out.println("Exception thrown : " + e);
        }
    }
}

Output:

argument is null 
Exception thrown : java.lang.NullPointerException: formatToCharacterIterator must be passed non-null object

Reference: https://docs.oracle.com/javase/9/docs/api/java/text/MessageFormat.html#formatToCharacterIterator-java.lang.Object-