Java Tutorial/Development/Formatter Specifiers

%a: Floating-point hexadecimal

   <source lang="java">

import java.util.Formatter; public class MainClass {

 public static void main(String args[]) {
   Formatter fmt = new Formatter();
   fmt.format("%a", 123.123);
   System.out.println(fmt);
 }

}</source>

0x1.ec7df3b645a1dp6

Formatter with different data types

   <source lang="java">

import java.util.Formatter; class FormatDemo {

 public static void main(String args[]) {
   Formatter fmt = new Formatter();
   fmt.format("Formatting %s is easy %d %f", "with Java", 10, 98.6);
   System.out.println(fmt);
 }

}</source>

Formatting Output with Formatter

   <source lang="java">

import java.util.Formatter; public class MainClass {

 public static void main(String args[]) {
   Formatter fmt = new Formatter();
   fmt.format("Formatting %s is easy %d %f", "with Java", 10, 98.6);
   
   System.out.println(fmt.toString());
 }

}</source>

Formatting with Java is easy 10 98.600000

Hex: %x, Octal: %o: Integer hexadecimal, Octal integer

   <source lang="java">

import java.util.Formatter; public class MainClass {

 public static void main(String args[]) {
   Formatter fmt = new Formatter();
   fmt.format("Hex: %x, Octal: %o", 196, 196);
   System.out.println(fmt);
 }

}</source>

Hex: c4, Octal: 304 *

%h: Hash code of the argument

   <source lang="java">

import java.util.Calendar; import java.util.Formatter; public class MainClass {

 public static void main(String args[]) {
   Formatter fmt = new Formatter();
   Calendar cal = Calendar.getInstance();
   
   fmt = new Formatter();
   fmt.format("%h", cal);
   System.out.println(fmt);
 }

}</source>

75ed2f99

The Format Specifiers

Format SpecifierConversion Applied%a and %AFloating-point hexadecimal%bBoolean%B%cCharacter%C%dDecimal integer%hHash code of the argument%H%eScientific notation%E%fDecimal floating point%gUses %e or %f, whichever is shorter%G%oOctal integer%nInserts a newline character%sString%S%tTime and date%T%xInteger hexadecimal%%Inserts a % sign

The %g format specifier causes Formatter to use either %f or %e, whichever is shorter

   <source lang="java">

import java.util.Formatter; public class MainClass {

 public static void main(String args[]) {
   Formatter fmt = new Formatter();
   for (double i = 1000; i < 1.0e+10; i *= 100) {
     fmt.format("%g ", i);
     System.out.println(fmt);
   }
 }

}</source>

1000.00 
1000.00 100000 
1000.00 100000 1.00000e+07 
1000.00 100000 1.00000e+07 1.00000e+09

The # symbol shows a digit or nothing if no digit present

   <source lang="java">

import java.text.DecimalFormat; import java.text.Format; public class Main {

 public static void main(String[] argv) throws Exception {
   Format formatter = new DecimalFormat("##");
   String s = formatter.format(-1234.567);
   System.out.println(s);
   s = formatter.format(0);
   System.out.println(s);
 }

}</source>

Unknown Format Conversion Exception

   <source lang="java">

import java.util.Date; import java.util.Formatter; public class MainClass {

 public static void main(String args[]) {
   Formatter fmt = new Formatter();
   fmt.format("%t", new Date());
   System.out.println(fmt);
 }

}</source>

Exception in thread "main" java.util.UnknownFormatConversionException: Conversion = "t"
  at java.util.Formatter$FormatSpecifier.<init>(Formatter.java:2646)
  at java.util.Formatter.parse(Formatter.java:2477)
  at java.util.Formatter.format(Formatter.java:2411)
  at java.util.Formatter.format(Formatter.java:2364)
  at MainClass.main(MainClass.java:8)

Use Formatter to left-justify strings within a table.

   <source lang="java">

import java.util.Formatter; public class Main {

 public static void main(String args[]) {
   Formatter fmt = new Formatter();
   fmt.format("%-12s %12s\n\n", "Source", "Loss");
   fmt.format("%-12s %,12d\n", "Retail", 1232675);
   System.out.println(fmt);
 }

} /* Source Loss Retail 1,232,675

• /</source>

Use Formatter to vertically align numeric values.

   <source lang="java">

import java.util.Formatter; public class Main {

 public static void main(String[] argv) throws Exception {
   double data[] = { 12.3, 45.6, -7.89, -1.0, 1.01 };
   Formatter fmt = new Formatter();
   fmt.format("%12s %12s\n", "Value", "Cube Root");
   for (double v : data) {
     fmt.format("%12.4f %12.4f\n", v, Math.cbrt(v));
   }
   System.out.println(fmt);
 }

} /* Value Cube Root

    12.3000       2.3084
    45.6000       3.5726
    -7.8900      -1.9908
    -1.0000      -1.0000
     1.0100       1.0033

• /</source>

Using group separators.

   <source lang="java">

import java.util.Formatter; public class Main {

 public static void main(String[] argv) throws Exception {
   Formatter fmt = new Formatter();
   fmt.format("No group separators: %d\n", 123456789);
   fmt.format("With group separators: %,d\n\n", 123456789);
   System.out.println(fmt);
 }

} /*No group separators: 123456789 With group separators: 123,456,789

• /</source>

using the %t specifier with Formatter.

   <source lang="java">

import java.util.Calendar; import java.util.Formatter; public class Main {

 public static void main(String[] argv) throws Exception {
   Formatter fmt = new Formatter();
   Calendar cal = Calendar.getInstance();
   // Display 12-hour time format.
   fmt.format("Time using 12-hour clock: %tr\n", cal);
   System.out.println(fmt);
 }

} //Time using 12-hour clock: 03:00:51 PM</source>