MessageFormat setFormatsByArgumentIndex() method in Java with Example

The setFormatsByArgumentIndex method of java.text.MessageFormat class is used to set the array of new format element in the pattern of message format object by overriding the old pattern.

Syntax:

public void setFormatsByArgumentIndex(Format[] newFormats)

Parameter: This method takes an array of format element as a parameter for overriding the old pattern of message format object.

Return Value: This method has nothing to return.

Exception: This method throws NullPointerException if array of new format element is null.

Below are the examples to illustrate the setFormatsByArgumentIndex() method:

Example 1:

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

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

public class GFG {
    public static void main(String[] argv)
    {
        try {
            // creating and initializing  MessageFormat
            MessageFormat mf
                = new MessageFormat("{0, date, #}, {2, number, #.##}, {4, time}");

            // display the current message format object
            displayFormat(mf);

            // creating and initializing new Format object array
            Format[] format = { new SimpleDateFormat("YYYY-'W'ww-u"),
                                new DecimalFormat("10.5678") };

            // settting the new array of formats
            // in the pattern of MessageFormat object
            // using setFormatsByArgumentIndex() method
            mf.setFormatsByArgumentIndex(format);

            // display the Override MessageFormat object
            System.out.println();
            displayFormat(mf);
        }
        catch (NullPointerException e) {
            System.out.println("format array is null");
            System.out.println("Exception thrown : " + e);
        }
    }

    // Defining displayFormat method
    public static void displayFormat(MessageFormat mf)
    {

        // display the result
        System.out.println("pattern : "
                           + mf.toPattern());

        // getting all format
        // used in MessageFormat Object
        // using getFormats() method
        Format[] formats = mf.getFormats();

        // display the result
        System.out.println("Required Formats are : ");
        for (int i = 0; i < formats.length; i++)
            System.out.println(formats[i]);
    }
}

Output:

pattern : {0, date, #}, {2, number, #0.##}, {4, time}
Required Formats are : 
java.text.SimpleDateFormat@403
java.text.DecimalFormat@674fc
java.text.SimpleDateFormat@8400729

pattern : {0, date, YYYY-'W'ww-u}, {2, number, #0.##}, {4, time}
Required Formats are : 
java.text.SimpleDateFormat@d21287d2
java.text.DecimalFormat@674fc
java.text.SimpleDateFormat@8400729

Example 2:

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

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

public class GFG {
    public static void main(String[] argv)
    {
        try {
            // creating and initializing  MessageFormat
            MessageFormat mf
                = new MessageFormat("{0, date, #}, {2, number, #.##}, {4, time}");

            // display the current message format object
            displayFormat(mf);

            // creating and initializing new Format object array
            Format[] format = { new SimpleDateFormat("YYYY-'W'ww-u"),
                                new DecimalFormat("10.5678") };

            // settting the new array of formats
            // in the pattern of MessageFormat object
            // using setFormatsByArgumentIndex() method
            mf.setFormatsByArgumentIndex(null);

            // display the Override MessageFormat object
            System.out.println();
            displayFormat(mf);
        }
        catch (NullPointerException e) {
            System.out.println("\nformat array is null");
            System.out.println("Exception thrown : " + e);
        }
    }

    // Defining displayFormat method
    public static void displayFormat(MessageFormat mf)
    {

        // display the result
        System.out.println("pattern : "
                           + mf.toPattern());

        // getting all format
        // used in MessageFormat Object
        // using getFormats() method
        Format[] formats = mf.getFormats();

        // display the result
        System.out.println("Required Formats are : ");
        for (int i = 0; i < formats.length; i++)
            System.out.println(formats[i]);
    }
}

Output:

pattern : {0, date, #}, {2, number, #0.##}, {4, time}
Required Formats are : 
java.text.SimpleDateFormat@403
java.text.DecimalFormat@674fc
java.text.SimpleDateFormat@8400729

format array is null
Exception thrown : java.lang.NullPointerException

Reference: https://docs.oracle.com/javase/9/docs/api/java/text/MessageFormat.html#setFormatsByArgumentIndex-java.text.Format:A-