MessageFormat setFormatByArgumentIndex() method in Java with Example

The setFormatByArgumentIndex() method of java.text.MessageFormat class is used to set the new format element at the particular index in pattern of message format object by overriding the previous pattern.

Syntax:

public void setFormatByArgumentIndex(int argumentIndex,
                                     Format newFormat)

Parameters: This method takes the following argument as a parameter.  

• argumentIndex :- this is the particular index where new format element is going to be placed.
• newFormat :- this is the new Format element which is going to be placed.

Return Value: This method has nothing to return.
Below are the examples to illustrate the setFormatByArgumentIndex() method:
Example 1:

Java

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

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

public class GFG {
    public static void main(String[] argv)
    {
        // creating and initializing  MessageFormat
        MessageFormat mf
            = new MessageFormat("{1, date, #}, {3, number, #.##}, {5, time}");

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

        // getting all the format element
        // used in MessageFormat Object
        Format[] formats = mf.getFormatsByArgumentIndex();

        // setting the new format element
        // at particular index
        // using setFormatByArgumentIndex() method
        for (int i = 0; i < formats.length; i++)
            mf.setFormatByArgumentIndex(i, formats[1]);

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

Output:

old pattern : {1,date, #}, {3,number, #0.##}, {5,time}

new pattern : {1,date, #}, {3,date, #}, {5,date, #}

Example 2:

Java

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

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

public class GFG {
    public static void main(String[] argv)
    {
        // creating and initializing  MessageFormat
        MessageFormat mf
            = new MessageFormat("{1, date, #}, {3, number, #.##}, {5, time}");

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

        // creating and initializing new Format element
        Format fm = NumberFormat.getInstance();

        // setting the new format element
        // at particular index
        // using setFormatByArgumentIndex() method
        for (int i = 0; i < 6; i++)
            mf.setFormatByArgumentIndex(i, fm);

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

Output:

old pattern : {1,date, #}, {3,number, #0.##}, {5,time}

new pattern : {1,number}, {3,number}, {5,number}

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