Use of Java string. Format

Formatted as the name suggests.

In jdk1.5, a useful static method string. Format () is added to the string class ():
Format (locale L, string format, object... ARGs) returns a formatted string using the specified language environment, format string, and parameters.
Format (string format, object... ARGs) returns a formatted string using the specified format string and parameters.

Here are some practical examples of this method (the comment is the output result ):

Code:

Long Now = system. currenttimemillis ();

String S = string. Format ("% TR", now); // "15:12"

Code:

// Current month/day/year

Date d = new date (now );

S = string. Format ("% TD", d); // "07/13/04"

Code:

S = string. Format ("%, D", integer. max_value); // "2,147,483,647"

Code:

S = string. Format ("% 05d", 123); // "00123" is it very convenient and exciting? Haha, there are more results!

In fact, the format function is similar to the printf function in C language. Some format strings are similar to C, but some customization has been made to adapt to the Java language and some of these features have been used. This method supports layout alignment and arrangement, as well as regular formats of numeric values, strings, and date/time data, and output in a specific language environment. Supports common Java types such as byte, bigdecimal, and calendar.

Each method that generates formatted output requires the format string and parameter list. A format string is a string that can contain fixed text and one or more embedded format specifiers. Consider the following example:

Calendar c = ...;
String S = string. Format ("Duke's birthday: % 1 $ TM % 1 $ te, % 1 $ ty", C );

The format string is the first parameter of the format method. It contains three format specifiers: "% 1 $ TM", "% 1 $ te", and "% 1 $ ty ", they indicate how parameters should be processed and where the text is inserted. The rest of the format string is fixed text that includes "Dukes birthday:" and any other space or punctuation. The parameter list consists of all parameters passed to the method after the format string. In the preceding example, the parameter list size is 1, which is composed of the new object calendar.

1. syntax for regular, character, and numeric format specifiers: % [argument_index $] [flags] [width] [. Precision] Conversion

The optional argument_index is a decimal integer used to indicate the position of a parameter in the parameter list. The first parameter is referenced by "1 $", the second parameter is referenced by "2 $", and so on.
The optional flags are character sets that modify the output format. The set of valid flag depends on the Conversion Type.
Optional width is a non-negative decimal integer, indicating the minimum number of characters to write to the output.
The optional precision is a non-negative decimal integer, which is usually used to limit the number of characters. The specific action depends on the Conversion Type.
The required conversion is a character that indicates how to format parameters. The valid conversion set of a given parameter depends on the Data Type of the parameter.

2. the syntax used to indicate format specifiers of Date and Time types is as follows:
% [Argument_index $] [flags] [width] Conversion

Optional argument_index, flags, and width are defined as the same.
The required conversion is a sequence of two characters. The first character is 'T' or 'T '. The second character indicates the format used. These characters are similar to but not completely equivalent to those defined by GNU date and POSIX strftime (3C.

3. syntax for format specifiers that do not correspond to parameters:
% [Flags] [width] Conversion

The optional flags and width definitions are the same as above.
The required conversion is a character that indicates the content to be inserted in the output.

Conversion
Conversion can be divided into the following types:
1. General-applicable to any parameter type
2. Character-it can be applied to the basic types of Unicode characters: Char, character, byte, byte, short, and short. When character. isvalidcodepoint (INT) returns true, you can apply this conversion to int and integer types.
3. Value
1. integer-integer types that can be applied to Java: byte, byte, short, short, Int, integer, long, long, And biginteger
2. Floating Point-applicable to Java floating point types: float, float, Double, double, and bigdecimal
4. date/time-types that can be applied to Java and can be encoded for date or time: Long, long, calendar, and date.
5. Percentage-generate the nominal value '%' ('/u0025 ')
6. Line separator-generate a platform-specific line Separator

The following table summarizes the supported conversions. It consists of uppercase characters (such as 'B', 'h', 's', 'C', 'x', 'E', 'G', 'A', and 'T') the conversion of the representation is equivalent to the conversion of the corresponding lower-case characters, except for converting the result to the upper-case form according to the popular locale rules. The latter is equivalent to the following calls of string. touppercase.

Description of conversion parameter categories
'B', 'B'. If the ARG parameter is null, the result is "false ". If Arg is a Boolean value or Boolean, the returned string is string. valueof. Otherwise, the result is "true ".
'H', 'H'. If the ARG parameter is null, the result is "null ". Otherwise, the result is obtained by calling integer. tohexstring (Arg. hashcode.
'S', 'S'. If the ARG parameter is null, the result is "null ". If Arg implements formattable, Arg. formatto is called. Otherwise, the result is obtained by calling Arg. tostring.
'C', 'C' returns a Unicode Character
The 'd' integer is formatted as a decimal integer.
The 'O' integer is formatted as an octal integer.
'X', 'x' integer result is formatted as a hexadecimal integer
'E', 'E' floating point result is formatted as a decimal number expressed in the computer science notation
'F' the floating point result is formatted as a decimal number.
'G' and 'G' floating point are formatted in computer scientific notation or decimal format based on the value after precision and rounding.
'A', 'A' floating point result is formatted as a hexadecimal floating point number with valid digits and Indexes
The prefix of the 'T', 't' date/time Date and Time Conversion characters. See date/time conversion.
'%' Percentage result is the nominal value '%' ('/u0025 ')
The 'n' line separator result is a platform-specific line separator.

Any character not explicitly defined as a conversion is invalid and is retained for future extension.

Date/time Conversion
The following Date and Time conversion suffixes are defined for 'T' and 'T' conversion. These types are similar to but not exactly equivalent to those defined by GNU date and POSIX strftime (3C. Other conversion types are provided to access Java-specific functions (for example, using 'l' as the millisecond in seconds ).

The following Conversion characters are used to format the time:

The hour in the 'H' 24-hour format is formatted as two digits with leading zeros (00-23) if necessary.
The hour in the 'I' 12-hour format is formatted as the two digits with the leading zero when necessary, that is, 01-12.
The hour in the 'K' 24-hour format, that is, 0-23.
Hours in the 'l' 12-hour format, that is, 1-12.
Minutes in the 'M' hour are formatted as two digits with leading zeros (00-59) if necessary.
Seconds in 's' minutes are formatted as two digits with leading zeros when necessary, that is, 00-60 ("60" is a special value required to support leap seconds ).
The millisecond in 'l' seconds is formatted as a three-digit number with leading zero when necessary, that is, 000-999.
The millisecond In 'n' seconds is formatted as the nine-digit number with the leading zero when necessary, that is, 000000000-999999999.
'P' indicates the language environment in lowercase in the morning or afternoon, for example, "am" or "PM ". You can use the conversion prefix 'T' to forcibly convert the output to an upper-case format.
The offset of 'Z' to the digital time zone in RFC 822 format of GMT, for example,-0800.
'Z' indicates a string in the abbreviated form of time zone. The formatter language environment replaces the parameter language environment (if any ).
The number of seconds since the Coordinated Universal Time (UTC) on January 1, 1970 00:00:00 to the present, that is, the difference between long. min_value/1000 and long. max_value/1000.
'Q' indicates the number of milliseconds that have elapsed since 00:00:00 on January 1, January 1, 1970 in Coordinated Universal Time (UTC), that is, the difference between long. min_value and long. max_value.

The following Conversion characters are used to format the date:

'B' is the full name of the month specific to the language environment, such as "January" and "February ".
'B' indicates the abbreviation of the month specific to the language environment, such as "Jan" and "FEB ".
'H' is the same as 'B.
'A is the full name of the day of the week specific to the language environment, such as "Sunday" and "Monday"
'A refers to the day of the week (such as "sun" and "mon") specific to the language environment"
'C' is divided by four digits of 100 to indicate the year. It is formatted as two digits with leading zeros (00-99) if necessary.
'Y' year, formatted as a four-digit (at least) with a leading zero when necessary, for example, 0092 equals 92 CE of the Gregorian calendar.
The last two digits of the 'y' year are formatted as the two digits with the leading zero when necessary, that is, 00-99.
The number of days in a year of 'J' is formatted as a three-digit number with a leading zero when necessary. For example, for a Gregorian calendar, the value is 001-366.
The 'M' month is formatted as a two-digit with a leading zero when necessary, that is, 01-13.
'D' the number of days in a month, which is formatted as the first zero or two digits (01-31) if necessary.
The number of days in a month is formatted as two digits, that is, 1-31.

The following Conversion characters are used to format common date/time combinations.

'R' 24-hour time, formatted as "% TH: % TM"
The time in the 'T' 24-hour format is formatted as "% TH: % TM: % ts ".
'R' 12-hour time, formatted as "% Ti: % TM: % TS % TP ". The location marked in the morning or afternoon ('% TP') may be related to the language environment.
'D' date, formatted as "% TM/% TD/% ty ".
'F' complete date in ISO 8601 format, formatted as "% ty-% TM-% TD ".
'C' date and time, formatted as "% TA % TB % TD % TT % TZ % ty", for example, "Sun Jul 20 16:17:00 EDT 1969 ".

Any character not explicitly defined as a conversion is invalid and is retained for future extension.

Flag
The following table summarizes the supported labels. Y indicates that the flag is supported by the indicated parameter type.

Marker general character integer floating point date/time Description
'-' Y the result is left aligned.
'#'Y1-Y3 y-the result should depend on the replacement form of the Conversion Type
'+ '-