String format(String format, Object... args)
The format specifiers for general, character, and numeric types have the following syntax:
%[argument_index$][flags][width][.precision]conversion
- argument_index is a decimal integer indicating the position of the argument in the argument list. It starts from "1$".
- flags is a set of characters that modify the output format.
| Flag | General | Character | Integer | Floating Point | Date/Time | Description |
| '-' | Y | Y | Y | Y | Y | The result will be left-justified |
| '#' | Y | - | Y | Y | - | The result should use a conversion-dependent alternate form |
| '+' | - | - | Y | Y | - | The result will always include a sign |
| ' ' | - | - | Y | Y | - | The result will include a leading space for positive values |
| '0' | - | - | Y | Y | - | The result will be zero-padded |
| ',' | - | - | Y | Y | - | The result will include locale-specific grouping separators |
| '(' | - | - | Y | Y | - | The result will enclose negative numbers in parentheses |
- width is a non-negative decimal interger indicating the minimum number of the number of characters to be written to the output.
- For the floating-point conversions
'e', 'E', and 'f' the precision is the number of digits after the decimal separator. If the conversion is 'g' or 'G', then the precision is the total number of digits in the resulting magnitude after rounding. If the conversion is 'a' or 'A', then the precision must not be specified. - conversion are divided into the following categories:
General, Character, Numeric(Integer, Floating Point), Date/Time, Percent, Line Separator
| Conversion | Argument Category | Description |
|---|
'b', 'B' | general | If the argument arg is null, then the result is "false". If arg is a boolean or Boolean, then the result is the string returned by String.valueOf(arg). Otherwise, the result is "true". |
'h', 'H' | general | If the argument arg is null, then the result is "null". Otherwise, the result is obtained by invoking Integer.toHexString(arg.hashCode()). |
's', 'S' | general | If the argument arg is null, then the result is "null". If arg implements Formattable, then arg.formatTo is invoked. Otherwise, the result is obtained by invokingarg.toString(). |
'c', 'C' | character | The result is a Unicode character |
'd' | integral | The result is formatted as a decimal integer |
'o' | integral | The result is formatted as an octal integer |
'x', 'X' | integral | The result is formatted as a hexadecimal integer |
'e', 'E' | floating point | The result is formatted as a decimal number in computerized scientific notation |
'f' | floating point | The result is formatted as a decimal number |
'g', 'G' | floating point | The result is formatted using computerized scientific notation or decimal format, depending on the precision and the value after rounding. |
'a', 'A' | floating point | The result is formatted as a hexadecimal floating-point number with a significand and an exponent |
't', 'T' | date/time | Prefix for date and time conversion characters. See Date/Time Conversions. |
'%' | percent | The result is a literal '%' ('\u0025') |
'n' | line separator | The result is the platform-specific line separator |
原标题：String.format Tutorial
关键词：string
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