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Text lesson

printf()

Example

The %s symbol serves as a placeholder for the string “World”.

System.out.printf(“Hello %s!”, “World”);

Note: Additional “Try it Yourself” examples are available at the bottom of this page.

Definition and Usage

The printf() method outputs formatted text or values to the console by using a format string along with additional arguments.

The data from these additional arguments is formatted and inserted into placeholders within the format string, indicated by a % symbol. The formatting of the arguments is determined by the sequence of characters following the % symbol.

Placeholders

The placeholders follow the format %[arg$][flags][width][.precision]conversion, where components in [square brackets] are optional.

Here’s a breakdown of each component:

arg$: Optional. A number followed by a $ sign that specifies which additional argument to use, starting with 1. This can be replaced with a < to use the previous argument.
flags: Optional. A sequence of any of the following characters:
–: Left-justifies the output by adding padding spaces to the right instead of the left.
+ : Prefixes positive numbers with “+”.
(space) : Prefixes a space to positive numbers for alignment with negative numbers.
0 : Pads numbers with zeros on the left.
, : Groups digits with separators (e.g., thousands separator).
width: Optional. A whole number specifying the minimum number of characters the output should occupy. Padding spaces are added to the right or to the left if the – flag is used.
.precision: Optional. A dot followed by a whole number indicating the number of decimal digits to show.
conversion: Required. A character that indicates how the argument’s data should be formatted. Uppercase characters format the data in uppercase where applicable. The possible characters are listed in the table below.

List of conversions

Character	Conversion	Description
`%`	Percent	Outputs a literal “%” character in the result.
`n`	Line break	Inserts a line break in the output.
`b` or `B`	Boolean	Shows the boolean value of an argument as “true” or “false”. If “B” is used, it displays “TRUE” or “FALSE” instead.
`c` or `C`	Unicode character	Displays the Unicode character representation of the argument. For whole numbers, this corresponds to the Unicode character associated with the number. If “C” is used, the character will be converted to uppercase where applicable.
`s` or `S`	String	Shows the default string representation of the argument. If “S” is used, the string will be converted to uppercase where possible.
`d`	Decimal integer	Expresses a whole number as a decimal integer.
`h` or `H`	Unsigned hexadecimal integer	Expresses an argument’s binary data as an unsigned hexadecimal integer. If “H” is used, digits A to F are displayed in uppercase. Please note that for any data other than positive integers, this representation does not reflect its actual value.
`o`	Octal integer	Represents a whole number as an octal integer. When the “#” flag is used, the number will be prefixed with “0”.
`x` or `X`	Hexadecimal integer	Represents a whole number as a hexadecimal integer. When the “#” flag is used, the number is prefixed with “0x”. If “X” is used, digits A to F and the letter X are displayed in uppercase.
`e` or `E`	Scientific notation	Represents a floating-point number in scientific notation. Using “E” will ensure that the letter “E” in the representation is uppercase. The “#” flag will enforce a decimal point even if there are no decimal digits.
`f`	Floating point number	Represents a floating-point number. When the “#” flag is used, it will ensure a decimal point is included even if there are no decimal digits.
`g` or `G`	General number	Displays the shortest representation for a floating-point number, choosing between “f” and “e” or “E”.
`a` or `A`	Hexadecimal floating point number	Display the internal representation of a floating-point number using hexadecimal digits.
`t` or `T`	Time or date	Displays a formatted date or time. If “T” is used, text parts such as “JANUARY” will be in uppercase. The following characters are available for date and time formatting: H: 24-hour format of an hour (00 to 23) I: 12-hour format of an hour (01 to 12) k: 24-hour format of an hour (0 to 23) l (lowercase ‘L’): 12-hour format of an hour (1 to 12) M: Minutes with leading zeros (00 to 59) S: Seconds with leading zeros (00 to 59) (may include 60 for leap seconds) L: Milliseconds with leading zeros (000 to 999) N: Nanoseconds with leading zeros (000000000 to 999999999) p: “am”, “pm”, “AM”, or “PM” to indicate morning or afternoon z: Difference to Greenwich time (Example: -0800) Z: Timezone abbreviations (Examples: EST, MDT) s: Seconds since the Unix Epoch (January 1, 1970 00:00:00 GMT) Q: Milliseconds since the Unix Epoch (January 1, 1970 00:00:00 GMT) B: Full textual representation of a month (January through December) b or h: Short textual representation of a month (three letters) A: Full textual representation of a day (Example: Monday) a: Short textual representation of a day (Example: Mon) C: The first two digits of the year (For 1970, “19” would be shown) Y: Four-digit representation of a year y: Two-digit representation of a year j: Day of the year with leading zeros (001 to 366) m: Numeric representation of a month (01 to 12) d: Day of the month (01 to 31) e: Day of the month without leading zeros (1 to 31) R: Time in 24-hour format (Example: 21:30) T: Time in 24-hour format with seconds (Example: 21:30:02) r: Time in 12-hour format with seconds (Example: 09:30:02 PM) (“AM” and “PM” are always uppercase) D: Date representation as month/day/year (Example: 12/17/23) F: Date representation as year-month-day (Example: 2023-12-17) c: Full date and time (Example: Thu Mar 28 10:51:00 EDT 2024)

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	Mandatory. A string comprising placeholders for the additional arguments, specifying the desired formatting for each.
args	Optional. Any number of supplementary arguments passed to the method, with their values formatted and exhibited according to the formatString.

Technical Details

Returns:	An object of type PrintStream.
Throws:	An IllegalFormatException occurs if the format string contains an invalid placeholder or if a placeholder is incompatible with the data type of the argument.
Java version:	1.5

More Examples

Example

Output a formatted text comprising a string and an integer.

System.out.printf(“Hello %s! One kilobyte is %,d bytes.”, “World”, 1024);

Example

Present a floating-point number using various formats.

// 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 that incorporates every element.

System.out.printf(“%2$,3.2f %1$s”, “meters”, 1260.5052);

Here’s the breakdown of each component in the placeholder %2$,3.2f:

2$: Denotes usage of the second argument’s value.
,: Specifies grouping of digits, typically by thousands.
3: Indicates a minimum length of 3 characters for the data representation.
.2: Specifies two digits after the decimal point.
f: Indicates the representation of data as a floating-point number.

Example

Convert a Unix timestamp into a formatted date.

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

Express characters using 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);