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下面是一些格式化参数说明(摘自Core Java 2 Volume I - Fundamentals, Seventh Edition)
Table 3-5. Conversions for printf
Conversion Character | Type | Example | d | Decimal integer | 159 | x | Hexadecimal integer | 9f | o | Octal integer | 237 | f | Fixed-point floating-point | 15.9 | e | Exponential floating-point | 1.59E+01 | g | General floating-point (the shorter of e and f) |
| a | Hexadecimal floating point | 0x1.fccdp3 | s | String | Hello | c | Character | H | b | Boolean | TRUE | h | Hash code | 42628b2 | tx | Date and time | See Table 3-7 | % | The percent symbol | % | n | The platform-dependent line separator |
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Table 3-7. Date and Time Conversion Characters Conversion Character | Type | Example | C | Complete date and time | Mon Feb 09 18:05:19 PST 2004 | F | ISO 8601 date | 2004-02-09 | D | U.S. formatted date (month/day/year) | 02/09/2004 | T | 24-hour time | 18:05:19 | r | 12-hour time | 06:05:19 pm | R | 24-hour time, no seconds | 18:05 | Y | Four-digit year (with leading zeroes) | 2004 | y | Last two digits of the year (with leading zeroes) | 04 | C | First two digits of the year (with leading zeroes) | 20 | B | Full month name | February | b or h | Abbreviated month name | Feb | m | Two-digit month (with leading zeroes) | 02 | d | Two-digit day (with leading zeroes) | 09 | e | Two-digit day (without leading zeroes) | 9 | A | Full weekday name | Monday | a | Abbreviated weekday name | Mon | j | Three-digit day of year (with leading zeroes), between 001 and 366 | 069 | H | Two-digit hour (with leading zeroes), between 00 and 23 | 18 | k | Two-digit hour (without leading zeroes), between 0 and 23 | 18 | I | Two-digit hour (with leading zeroes), between 01 and 12 | 06 | l | Two-digit hour (without leading zeroes), between 1 and 12 | 6 | M | Two-digit minutes (with leading zeroes) | 05 | S | Two-digit seconds (with leading zeroes) | 19 | L | Three-digit milliseconds (with leading zeroes) | 047 | N | Nine-digit nanoseconds (with leading zeroes) | 047000000 | P | Uppercase morning or afternoon marker | PM | p | Lowercase morning or afternoon marker | pm | z | RFC 822 numeric offset from GMT | -0800 | Z | Time zone | PST | s | Seconds since 1970-01-01 00:00:00 GMT | 1078884319 | E | Milliseconds since 1970-01-01 00:00:00 GMT | 1078884319047 |
Table 3-6. Flags for printf Flag | Purpose | Example | + | Prints sign for positive and negative numbers | +3333.33 | space | Adds a space before positive numbers | | 3333.33| | 0 | Adds leading zeroes | 003333.33 | - | Left-justifies field | |3333.33 | | ( | Encloses negative number in parentheses | (3333.33) | , | Adds group separators | 3,333.33 | # (for f format) | Always includes a decimal point | 3,333. | # (for x or o format) | Adds 0x or 0 prefix | 0xcafe | ^ | Converts to upper case | 0XCAFE | $ | Specifies the index of the argument to be formatted; for example, %1$d %1$x prints the first argument in decimal and hexadecimal | 159 9F | < | Formats the same value as the previous specification; for example, %d %<x prints the same number in decimal and hexadecimal |
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这里是一些简单的介绍，更详细的说明请参考： Core Java 2 Volume I - Fundamentals, Seventh Edition Core Java 2 Volume II - Advanced Features, Seventh Edition 里面都有一些很精彩的描述，中文名称就是《Java核心技术》。只有第七版才有J2SE5.0的介绍，但是第七版好像还没有中文版。本文还参考了Professional Java JDK - 5th Edition.
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