fast-printf

fast-printf is a Java library for fast printf-like formatting. Features:

• Can be extremely fast , about 4x faster than String.format.
• Compatible with glibc printf convention, rather than Java String.format convention.
• Zero dependency. No external dependencies, requires only Java 8+.

Usage

<dependency>
    <groupId>io.github.yuyuzha0</groupId>
    <artifactId>fast-printf</artifactId>
    <version>1.1.0</version>
</dependency>

import java.time.LocalDateTime;

import io.fastprintf.Args;
import io.fastprintf.FastPrintf;

public class Usage {
    public void usage() {
        // The `FastPrintf` instance should be created once and reused.
        FastPrintf fastPrintf = FastPrintf.compile("%#08X, %05.2f, %.5S, %{yyyy-MM-dd HH:mm:ss}t");
        LocalDateTime dateTime = LocalDateTime.of(2023, 12, 31, 23, 59, 59);

        String format = fastPrintf.format(123456789L, Math.PI, "Hello World", dateTime);
        assertEquals("0X75BCD15, 03.14, HELLO, 2023-12-31 23:59:59", format);

        Args args = Args.of(123456789L, Math.PI, "Hello World", dateTime);
        assertEquals("0X75BCD15, 03.14, HELLO, 2023-12-31 23:59:59", fastPrintf.format(args));

        Args args1 =
                Args.create()
                        .putLong(123456789L)
                        .putDouble(Math.PI)
                        .putString("Hello World")
                        .putDateTime(dateTime);
        assertEquals("0X75BCD15, 03.14, HELLO, 2023-12-31 23:59:59", fastPrintf.format(args1));
    }
}

Spec

Syntax

%[flags][width][.precision][{date-time-pattern}]specifier

Specifiers

specifier	Output	Example
d or i	Signed decimal integer	392
u	Unsigned decimal integer	7235
o	Unsigned octal	610
x	Unsigned hexadecimal integer	7fa
X	Unsigned hexadecimal integer (uppercase)	7FA
f	Decimal floating point, lowercase	392.65
F	Decimal floating point, uppercase	392.65
e	Scientific notation (mantissa/exponent), lowercase	3.9265e+2
E	Scientific notation (mantissa/exponent), uppercase	3.9265E+2
g	Use the shortest representation: %e or %f	392.65
G	Use the shortest representation: %E or %F	392.65
a	Hexadecimal floating point, lowercase	-0xc.90fep-2
A	Hexadecimal floating point, uppercase	-0XC.90FEP-2
c	Character	a
s	String of characters	sample
S	String of characters, uppercase	SAMPLE
t	Date/Time string	2023-12-31 23:59:59
T	Date/Time string, uppercase	2023-12-31 23:59:59
p	Java Pointer address (Like Object.toString() output format)	java.lang.Integer@707f7052
n	Nothing printed.
%	A % followed by another % character will write a single % to the stream.	%

Flags

flags	description
-	Left align the result within the given field width.
+	Forces to preceed the result with a plus or minus sign (+ or -) even for positive numbers. By default, only negative numbers are preceded with a - sign.
(space)	Use a blank to prefix the output value if it's signed and positive. The blank is ignored if both the blank and + flags appear.
#	When it's used with the o, x, or X format, the # flag uses 0, 0x, or 0X, respectively, to prefix any nonzero output value. When it's used with the e, E, f, F, a, or A format, the # flag forces the output value to contain a decimal point. When it's used with the g or G format, the # flag forces the output value to contain a decimal point and prevents the truncation of trailing zeros. Ignored when used with c, d, i, u, or s.
0	If width is prefixed by 0, leading zeros are added until the minimum width is reached. If both 0 and - appear, the 0 is ignored. If 0 is specified for an integer format (i, u, x, X, o, d) and a precision specification is also present—for example, %04.d—the 0 is ignored. If 0 is specified for the a or A floating-point format, leading zeros are prepended to the mantissa, after the 0x or 0X prefix.

Width

width	description
(number)	Minimum number of characters to be printed. If the value to be printed is shorter than this number, the result is padded with blank spaces. The value is not truncated even if the result is larger.
*	The width is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted.

Precision

.precision	description
.number	For integer specifiers (d, i, o, u, x, X): precision specifies the minimum number of digits to be written. If the value to be written is shorter than this number, the result is padded with leading zeros. The value is not truncated even if the result is longer. A precision of 0 means that no character is written for the value 0. For a, A, e, E, f and F specifiers: this is the number of digits to be printed after the decimal point (by default, this is 6). For g and G specifiers: This is the maximum number of significant digits to be printed. For s: this is the maximum number of characters to be printed. By default all characters are printed until the ending null character is encountered. If the period is specified without an explicit value for precision, 0 is assumed.
.*	The precision is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted.