Formatted output in Java

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:

Without formattiing: PI = 3.141592653589793
Formatted to Give 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 : 16-10-2016
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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