Format Specifiers in Java

Last Updated : 06 Jul, 2020

Format specifiers begin with a percent character (%) and terminate with a “type character, ” which indicates the type of data (int, float, etc.) that will be converted the basic manner in which the data will be represented (decimal, hexadecimal, etc.)
The general syntax of a format specifier is

% [flags] [width] [.precision] [argsize] typechar

The format() method of Formatter class accepts a wide variety of format specifiers. When an uppercase specifier is used, then letters are shown in uppercase. Otherwise, the upper- and lowercase specifiers perform the same conversion.

Format Specifier	Conversion Applied
%%	Inserts a % sign
%x %X	Integer hexadecimal
%t %T	Time and Date
%s %S	String
%n	Inserts a newline character
%o	Octal integer
%f	Decimal floating-point
%e %E	Scientific notation
%g	Causes Formatter to use either %f or %e, whichever is shorter
%h %H	Hash code of the argument
%d	Decimal integer
%c	Character
%b %B	Boolean
%a %A	Floating-point hexadecimal

Space format specifier : When creating columns of numbers, it is sometimes very useful to print a space before a positive number so that positive and negative number get aligned. To do this, space format specifier can be used.

Syntax:

Formatter().format("% d", -111);
Formatter().format("% d", 111);

Output:
-111
 111

Example:

// Java program to demonstrate
// the space format specifier
  
import java.util.*;
  
class GFG {
    public static void main(String args[])
    {
  
        // create Formatter class object
        Formatter formatter = new Formatter();
  
        // Use Space format specifier
        formatter.format("%d", -111);
        System.out.println(formatter);
  
        formatter = new Formatter();
        formatter.format("% d", 111);
        System.out.println(formatter);
  
        formatter = new Formatter();
        formatter.format("% d", -222);
        System.out.println(formatter);
  
        formatter = new Formatter();
        formatter.format("% d", 222);
        System.out.println(formatter);
    }
}

Output:

+ Sign Specifier: This adds the + sign before positive numeric value, and has no effect on negative numeric value.

Syntax:

Formatter().format("%+d", 111);

Output:
+111

Example:

// Java program to demonstrate
// the + sign Specifier format specifiers.
  
import java.util.*;
  
class GFG {
    public static void main(String args[])
    {
  
        // create Formatter class object
        Formatter formatter = new Formatter();
  
        // + sign specifier
        formatter = new Formatter();
        formatter.format("%+d", 111);
        System.out.println(formatter);
  
        // + sign specifier
        // on - sign, it will have no effect
        formatter = new Formatter();
        formatter.format("%+d", -111);
        System.out.println(formatter);
    }
}

Output:

+111
-111

( specifier: This specifier puts the negative numeric values inside the parentheses, and has no effect on the positive numeric values.

Syntax:

Formatter().format("%(d", -111);
Formatter().format("%(d", 111);

Output:
(111)
111

Example:

// Java program to demonstrate
// the ( Specifiers format specifiers.
  
import java.util.*;
  
class GFG {
    public static void main(String args[])
    {
  
        // create Formatter class object
        Formatter formatter = new Formatter();
  
        // ( Specifier
        formatter = new Formatter();
        formatter.format("%(d", -111);
        System.out.println(formatter);
  
        formatter = new Formatter();
        formatter.format("%(d", 111);
        System.out.println(formatter);
    }
}

Output:

(111)
111

Comma, Specifier: For displaying large numbers, it is often useful to add grouping separators by comma (, ). For example, the value is 1000000 more easily read when formatted as 1, 000, 000. To add grouping specifiers (, ) use the comma(, ) Specifier.

Syntax:

Formatter().format("%, d", 1000000);

Output:
1, 000, 000

Example:

// Java program to demonstrate
// the comma format specifiers.
  
import java.util.*;
  
public class GFG {
    public static void main(String args[])
    {
  
        // create Formatter class object
        Formatter formatter = new Formatter();
  
        // comma Specifier
        formatter = new Formatter();
        formatter.format("%, d", 1000000);
        System.out.println(formatter);
  
        // comma Specifier
        formatter = new Formatter();
        formatter.format("%, .3f", 32659526566.4521);
        System.out.println(formatter);
    }
}

Output:

1, 000, 000
32, 659, 526, 566.452

Left Justification(-) Specifier: By default all output is right-shifted. That is, if the field width is longer than the data printed, data will be placed on the right side of the field. One can force output to be left-justified by placing a minus sign directly after the %. For instance, %-20.4f left justifies a floating-point number with two decimal places in a 20-character field.

Syntax:

Formatter().format("|%-20.4f|", 1234.1234);

Output:
|           1234.1234|
|1234.1234           |

Example:

// Java program to demonstrate
// the left justification format specifiers.
  
import java.util.*;
  
class GFG {
    public static void main(String args[])
    {
  
        // create Formatter class object
        Formatter formatter = new Formatter();
  
        // right justify by default
        formatter = new Formatter();
        formatter.format("|%20.4f|", 1234.1234);
        System.out.println(formatter);
  
        // left justify
        formatter = new Formatter();
        formatter.format("|%-20.4f|", 1234.1234);
        System.out.println(formatter);
    }
}

Output:

|           1234.1234|
|1234.1234           |

The %n format specifiers:
The %n format specifier is different from the others in that it doesn’t take arguments. It is simply an escape sequence that inserts a character into the output. The %n inserts a newline. It can’t be entered directly into the format string.

// Java program to demonstrate
// the newline %n format specifiers.
  
import java.util.*;
  
public class GFG {
    public static void main(String args[])
    {
        // create Formatter class object
        Formatter formatter = new Formatter();
  
        // newline format specifier
        formatter.format("Geeks %nFor %nGeeks");
  
        // Print the output
        System.out.println(formatter);
    }
}

Output:

Geeks 
For 
Geeks

The %% format specifiers:
The %% format specifier is different from the others in that it doesn’t take arguments. It is simply an escape sequence that inserts a character into the output. The %% inserts a % sign. It can’t be entered directly into the format string.

// Java program to demonstrate
// the %% format specifiers.
  
import java.util.*;
  
public class GFG {
    public static void main(String args[])
    {
        // create Formatter class object
        Formatter formatter = new Formatter();
  
        // %% format specifier
        formatter.format("10 %% 4 = 2");
  
        // Print the output
        System.out.println(formatter);
    }
}

Output:

10 % 4 = 2

The %x %X format specifiers:
The %x or %X format specifier is is used to represent the integer Hexadecimal value. %x displays the hexadecimal values with lowercase alphabets whereas the %X specifier displays the hexadecimal values with uppercase alphabets.

// Java program to demonstrate
// the integer-Hexadecimal %x and %X
// format specifiers.
  
import java.util.*;
  
public class GFG {
    public static void main(String args[])
    {
        // create Formatter class object
        Formatter formatter = new Formatter();
  
        // %x format specifier
        // It prints the number in Hexadecimal
        // with lowercase alphabets
        formatter.format("%x", 250);
  
        // Print the output
        System.out.println("LowerCase Hexadecimal"
                           + " using %x: "
                           + formatter);
  
        // %X format specifier
        // It prints the number in Hexadecimal
        // with uppercase alphabets
        formatter = new Formatter();
        formatter.format("%X", 250);
  
        // Print the output
        System.out.println("UpperCase Hexadecimal"
                           + " using %X: "
                           + formatter);
    }
}

Output:

LowerCase Hexadecimal using %x: fa
UpperCase Hexadecimal using %X: FA

The %e %E format specifiers:
The %e or %E format specifier is is used to represent the Scientific Notation of a value. %e displays the Scientific Notation with lowercase alphabets whereas the %E specifier displays the Scientific Notation with uppercase alphabets.

// Java program to demonstrate
// the Scientific Notation %e and %E
// format specifiers.
  
import java.util.*;
  
public class GFG {
    public static void main(String args[])
    {
        // create Formatter class object
        Formatter formatter = new Formatter();
  
        // %e format specifier
        // It prints the number in Scientific Notation
        // with lowercase alphabets
        formatter.format("%e", 123.1234);
  
        // Print the output
        System.out.println("LowerCase Scientific Notation"
                           + " using %e: "
                           + formatter);
  
        // %E format specifier
        // It prints the number in Scientific Notation
        // with uppercase alphabets
        formatter = new Formatter();
        formatter.format("%E", 123.1234);
  
        // Print the output
        System.out.println("UpperCase Scientific Notation"
                           + " using %E: "
                           + formatter);
    }
}

Output:

LowerCase Scientific Notation using %e: 1.231234e+02
UpperCase Scientific Notation using %E: 1.231234E+02

Precision Formats
A precision specifier can be applied to the %f, %e, %g, and %s format specifiers.

// Java program to demonstrate
// Prrecision Format specifiers
  
import java.util.Formatter;
  
public class GFG {
    public static void main(String args[])
    {
  
        // Create the Formatter instance
        Formatter formatter = new Formatter();
  
        // added floating-point data
        // using the %f or %e specifiers,
        // Format to 2 decimal places
        // in a 16 character field.
        formatter = new Formatter();
        formatter.format("%16.2e", 123.1234567);
        System.out.println("Scientific notation to 2 places: "
                           + formatter);
  
        // Format 4 decimal places.
        formatter = new Formatter();
        formatter.format("%.4f", 123.1234567);
        System.out.println("Decimal floating-point"
                           + " notation to 4 places: "
                           + formatter);
  
        // Format 4 places.
        // The %g format specifier causes Formatter
        // to use either %f or %e, whichever is shorter
        formatter = new Formatter();
        formatter.format("%.4g", 123.1234567);
        System.out.println("Scientific or Decimal floating-point "
                           + "notation to 4 places: "
                           + formatter);
  
        // Display at most 15 characters in a string.
        formatter = new Formatter();
        formatter.format("%.15s", "12345678901234567890");
        System.out.println("String notation to 15 places: "
                           + formatter);
  
        // Format into 10 digit
        formatter = new Formatter();
        formatter.format("%010d", 88);
        System.out.println("value in 10 digits: "
                           + formatter);
    }
}

Output:

Scientific notation to 2 places:         1.23e+02
Decimal floating-point notation to 4 places: 123.1235
Scientific or Decimal floating-point notation to 4 places: 123.1
String notation to 15 places: 123456789012345
value in 10 digits: 0000000088

Related Article : Format Specifiers in C

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