Java Output printf() Method
Example
Print some formatted text to the console.
The %s character is a placeholder for the string "World":
System.out.printf("Hello %s!", "World");Note: You will find more "Try it Yourself" examples at the bottom of this page.
Definition and Usage
The printf() method outputs a formatted string.
Data from the additional arguments is formatted and written into placeholders
in the formatted string, which are marked by a % symbol. The way in which arguments
are formatted depends on the sequence of characters that follows the % symbol.
Placeholders
The placeholders have the form %[arg$][flags][width][.precision]conversion. The components in [square brackets] are optional.
An explanation of each of the components:
arg$- Optional. A number followed by a $ sign which indicates which of the additional arguments to use, argument numbers start at 1. This can be replaced with a<which specifies that the argument from the previous placeholder should be used.flags- Optional. A sequence of any of the following characters:-- Makes the output left-justified by adding any padding spaces to the right instead of to the left.+- Causes positive numbers to always be prefixed with "+".0- Pads numbers with zeroes on the left.,- Groups digits (for example by thousands) and puts separators between the groups.
width- Optional. A whole number specifying the minimum number of characters that the output should occupy. If necessary spaces are added to the right to reach this number, or to the left if the-flag is used..precisionOptional. A.followed by a whole number indicating how many decimal digits to show in the formatted data.conversion- Required. A character which indicates how an argument's data should be represented. If the character is uppercase the data will be formatted in uppercase where possible. The list of possible characters is shown in the table below.
List of conversions
| Character | Conversion | Description |
|---|---|---|
% |
Percent | Displays a literal "%" character in the output. |
n |
Line break | Displays a line break in the output. |
b or B |
Boolean | Displays the boolean value of an argument as "true" or "false". If "B" is used then it displays "TRUE" or "FALSE" instead. |
c or C |
Unicode character | Displays a unicode character representation of the argument. For whole numbers, this is the unicode character that corresponds to the number. If "C" is used then the character will be converted to uppercase where possible. |
s or S |
String | Displays the default string representation of the argument. If "S" is used then the string will be converted to uppercase where possible. |
d |
Decimal integer | Represents a whole number as a decimal integer. |
h or H |
Unsigned hexadecimal integer |
Represents an argument's binary data as an unsigned hexadecimal integer. If "H" is used then digits A to F are shown in uppercase.
Note: For any data other than positive integers this does not represent its real value. |
o |
Octal integer | Represents a whole number as an octal integer. The "#" flag will prefix the number with "0". |
x or X |
Hexadecimal integer | Represents a whole number as a hexadecimal integer. The "#" flag will prefix the number with "0x". If "X" is used then digits A to F and the letter X are shown in uppercase. |
e or E |
Scientific notation | Represents a floating point number in scientific notation. If "E" is used then the letter "E" of the representation will be uppercase. The "#" flag will force a decimal point even if there are no decimal digits. |
f |
Floating point number | Represents a floating point number. The "#" flag will force a decimal point even if there are no decimal digits. |
g or G |
General number | Displays the shortest representation between f and e or E for a floating point number. |
a or A |
Hexadecimal floating point number | Display a floating point number's internal representation with hexadecimal digits. |
t or T |
Time or date |
Displays a formatted date or time. The t or T must be followed by one more character indicating how the date or time should be formatted. If "T" is used then text parts of a date or time such as "JANUARY" will be uppercase.
The following characters can be used for date and time formatting:
|
Syntax
System.out.printf(locale, formatString, args)Parameter Values
| Parameter | Description |
|---|---|
| locale | Optional. A locale used to determine some of the formatting, such as which characters are used for decimal points and grouping separators. |
| formatString | Required. A string containing placeholders for the additional arguments indicating how to format them |
| args | Optional. Any number of additional arguments to the method, their values can be formatted and displayed in the formatString. |
Technical Details
| Returns: | A PrintStream object. |
|---|---|
| Throws: | IllegalFormatException - if the format string contains an invalid placeholder or a placeholder isn't compatible with the data type of the argument. |
| Java version: | 1.5 |
More Examples
Example
Print a formatted text containing a string and an integer:
System.out.printf("Hello %s! One kilobyte is %,d bytes.", "World", 1024);Example
Format a floating point number in different ways:
// Default
System.out.printf("%f%n", 123456.78);
// Two decimal digits
System.out.printf("%.2f%n", 123456.78);
// No decimal digits
System.out.printf("%.0f%n", 123456.78);
// No decimal digits but keep the decimal point
System.out.printf("%#.0f%n", 123456.78);
// Group digits
System.out.printf("%,.2f%n", 123456.78);
// Scientific notation with two digits of precision
System.out.printf("%.2e", 123456.78);Example
A placeholder which uses all of the components:
System.out.printf("%2$,3.2f %1$s", "meters", 1260.5052);This is how each part of the placeholder %2$,3.2f works:
2$indicates that the value of the second argument is used,indicates that digits should be grouped (usually by thousands)3indicates that the representation of the data should be at least 3 characters long.2indicates that there should be two digits after the decimal pointfindicates that the data is being represented as a floating point number
Example
Use arguments in a different order:
System.out.printf("%3$c %2$c %1$c", 'a', 'b', 'c');Example
Format a date from a Unix timestamp:
long date = 1711638903488L; // Unix timestamp (number of milliseconds since January 1, 1970)
// Time
System.out.printf("%tl:%<tM %<tp%n", date);
// Month and day
System.out.printf("%tB %<te%n", date);
// Full date representation
System.out.printf("%tc%n", date);Example
Represent characters from their unicode code points:
// Represent characters from their unicode code points
System.out.printf("%c%c%c%c%c%n", 72, 101, 108, 108, 111);
// Force unicode characters to uppercase
System.out.printf("%C%C%C%C%C", 72, 101, 108, 108, 111);❮ Output Methods
