Sometimes in Competitive programming, it is essential to print the output in a given specified format. Most users are familiar with printf function in C. Let us discuss how we can format the output in Java.
There are different ways in which we can format output in Java. Some of them are given below.
- Using System.out.printf()
- Using DecimalFormat class
- Using SimpleDateFormat class (for formatting Dates)
1. Formatting output using System.out.printf()Â
This is the easiest of all methods as this is similar to printf in C. Note that System.out.print() and System.out.println() take a single argument, but printf() may take multiple arguments.
Java
// Java program to demonstrate working of printf()Â
class JavaFormatter1 {Â Â Â Â public static void main(String args[])Â Â Â Â {Â Â Â Â Â Â Â Â int x = 100;Â Â Â Â Â Â Â Â System.out.printf(Â Â Â Â Â Â Â Â Â Â Â Â "Printing simple integer: x = %d\n", x);Â
        // this will print it upto 2 decimal places        System.out.printf(            "Formatted with precision: PI = %.2f\n",            Math.PI);Â
        float n = 5.2f;Â
        // automatically appends zero to the rightmost part        // of decimal        System.out.printf(            "Formatted to specific width: n = %.4f\n", n);Â
        n = 2324435.3f;Â
        // here number is formatted from right margin and        // occupies a width of 20 characters        System.out.printf(            "Formatted to right margin: n = %20.4f\n", n);    }} |
Output
Printing simple integer: x = 100 Formatted with precision: PI = 3.14 Formatted to specific width: n = 5.2000 Formatted to right margin: n = 2324435.2500
Note: System.out.format() is equivalent to printf() and can also be used.
2. Formatting using DecimalFormat classÂ
DecimalFormat is used to format decimal numbers.
Java
// Java program to demonstrate working of DecimalFormatimport java.text.DecimalFormat;Â
class JavaFormatter2 {Â Â Â Â public static void main(String args[])Â Â Â Â {Â Â Â Â Â Â Â Â double num = 123.4567;Â
        // prints only numeric part of a floating number        DecimalFormat ft = new DecimalFormat("####");        System.out.println("Without fraction part: num = "                           + ft.format(num));Â
        // this will print it upto 2 decimal places        ft = new DecimalFormat("#.##");        System.out.println(            "Formatted to Give precision: num = "            + ft.format(num));Â
        // automatically appends zero to the rightmost part        // of decimal instead of #,we use digit 0        ft = new DecimalFormat("#.000000");        System.out.println(            "appended zeroes to right: num = "            + ft.format(num));Â
        // automatically appends zero to the leftmost of        // decimal number instead of #,we use digit 0        ft = new DecimalFormat("00000.00");        System.out.println(            "formatting Numeric part : num = "            + ft.format(num));Â
        // formatting money in dollars        double income = 23456.789;        ft = new DecimalFormat("$###,###.##");        System.out.println("your Formatted Dream Income : "                           + ft.format(income));    }} |
Output
Without fraction part: num = 123 Formatted to Give precision: num = 123.46 appended zeroes to right: num = 123.456700 formatting Numeric part : num = 00123.46 your Formatted Dream Income : $23,456.79
3. Formatting dates and parsing using SimpleDateFormat class
This class is present in java.text package.Â
Java
// Java program to demonstrate working of SimpleDateFormatÂ
import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.Date;Â
class Formatter3 {    public static void main(String args[])        throws ParseException    {        // Formatting as per given pattern in the argument        SimpleDateFormat ft            = new SimpleDateFormat("dd-MM-yyyy");        String str = ft.format(new Date());        System.out.println("Formatted Date : " + str);Â
        // parsing a given String        str = "02/18/1995";        ft = new SimpleDateFormat("MM/dd/yyyy");        Date date = ft.parse(str);Â
        // this will print the date as per parsed string        System.out.println("Parsed Date : " + date);    }} |
Output
Formatted Date : 24-01-2022 Parsed Date : Sat Feb 18 00:00:00 UTC 1995
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