Formatted output in Java

Difficulty Level : Medium
Last Updated : 09 Aug, 2018

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 see discuss how we can format the output in Java:

Formatting output using System.out.printf()
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.

// A Java program to demonstrate working of printf() in Java 
class JavaFormatter1 
{ 
  public static void main(String args[]) 
  { 
    int x = 100; 
    System.out.printf("Printing simple integer: x = %d\n", x); 
  
    // this will print it upto 2 decimal places 
    System.out.printf("Formatted with precison: PI = %.2f\n", Math.PI); 
  
    float n = 5.2f; 
  
    // automatically appends zero to the rightmost part of decimal 
    System.out.printf("Formatted to specific width: n = %.4f\n", n); 
  
    n = 2324435.3f; 
  
    // 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 precison: PI = 3.14
Formatted to specific width: n = 5.2000
Formatted to right margin: n =         2324435.2500

System.out.format() is equivalent to printf() and can also be used.

Formatting using DecimalFormat class:
DecimalFormat is used to format decimal numbers.

// Java program to demonstrate working of DecimalFormat 
import java.text.DecimalFormat; 
  
class JavaFormatter2 
{ 
  public static void main(String args[]) 
  { 
    double num = 123.4567; 
  
    // prints only numeric part of a floating number 
    DecimalFormat ft = new DecimalFormat("####"); 
    System.out.println("Without fraction part: num = " + ft.format(num)); 
  
    // this will print it upto 2 decimal places 
    ft = new DecimalFormat("#.##"); 
    System.out.println("Formatted to Give precison: num = " + ft.format(num)); 
  
    // 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)); 
  
    // 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)); 
  
    // 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 precison: num = 123.46
appended zeroes to right: num = 123.456700
formatting Numeric part : num = 00123.46
your Formatted Dream Income : $23,456.79

Formatting dates and parsing using SimpleDateFormat class:
This class is present in java.text package.

// Java program to demonstrate working of SimpleDateFormat 
import java.text.ParseException; 
import java.text.SimpleDateFormat; 
import java.util.Date; 
  
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); 
  
    // parsing a given String 
    str = "02/18/1995"; 
    ft = new SimpleDateFormat("MM/dd/yyyy"); 
    Date date = ft.parse(str); 
  
    // this will print the date as per parsed string 
    System.out.println("Parsed Date : " + date); 
  } 
} 

Output:

Formatted Date : 09-08-2018
Parsed Date : Sat Feb 18 00:00:00 UTC 1995

References:
https://docs.oracle.com/javase/tutorial/essential/io/formatting.html
https://docs.oracle.com/javase/tutorial/java/data/numberformat.html
http://docs.oracle.com/javase/6/docs/api/java/text/SimpleDateFormat.html

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