Java Format Specifier
Description
The format() method 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.
Specifier List
The following table shows the format specifiers:
| Format Specifier | Conversion Applied |
|---|---|
| %a %A | Floating-point hexadecimal |
| %b %B | Boolean |
| %c | Character |
| %d | Decimal integer |
| %h %H | Hash code of the argument |
| %e %E | Scientific notation |
| %f | Decimal floating-point |
| %g %G | Uses %e or %f, whichever is shorter |
| %o | Octal integer |
| %n | Inserts a newline character |
| %s %S | String |
| %t %T | Time and date |
| %x %X | Integer hexadecimal |
| %% | Inserts a % sign |
If the argument doesn't match the type-checks, an IllegalFormatException is thrown.
Example
Java Format Specifier
import java.util.Calendar;
import java.util.Formatter;
//from www .j av a2s.c om
public class Main {
public static void main(String args[]) {
Formatter fmt = new Formatter();
fmt = new Formatter();
System.out.println(fmt.format("%s gap filler %d %f", "Astring", 10, 12.3));
}
}
You can obtain a reference to the underlying output buffer by calling out().
It returns a reference to an Appendable object.
The code above generates the following result.
Example 2
Unknown Format Conversion Exception
import java.util.Date;
import java.util.Formatter;
/*from www.ja v a 2 s.c om*/
public class Main {
public static void main(String args[]) {
Formatter fmt = new Formatter();
fmt.format("%t", new Date());
System.out.println(fmt);
}
}
The code above generates the following result.
Example 3
The %n and %% format specifiers escape sequences.
The %n inserts a newline.
The %% inserts a percent sign.
You can use the standard escape sequence \n to embed a newline character.
Here is an example that demonstrates the %n and %% format specifiers:
import java.util.Formatter;
//from www . j av a 2s. c om
public class Main {
public static void main(String args[]) {
Formatter fmt = new Formatter();
fmt.format("line%nline %d%% complete", 88);
System.out.println(fmt);
}
}
The output:
Example 4
The following code combines the %n, %d %% to display file copy progress information.
import java.util.Formatter;
//from ww w. ja v a2 s . c om
public class Main {
public static void main(String args[]) {
Formatter fmt = new Formatter();
fmt.format("Copying file%nTransfer is %d%% complete", 88);
System.out.println(fmt);
}
}
The output:
