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java中的格式化输出(类似C语言的printf)

王朝java/jsp·作者佚名  2008-05-31
窄屏简体版  字體: |||超大  

前几天想在Java中用格式化输出,多亏rollingpig、zlzj2010等几位老大提示,现在我用text package中的NumberFormat和DecimalFomat实现了一把,给大家show一下,请多指教。

简单说明:

a.格式描述符:

1. L或l - 使数字左对齐(缺省是右对齐)

2. C或c - 使数字居中对齐(缺省是右对齐)

3. X或x - 显示数字为十六进制(缺省是十进制)

4. B或b - 显示数字为八进制(缺省是十进制)

5. ,(半角逗号)- 千位分隔符

6. S或s - 显示数字为科学记数法

7. Z或z - 用零填空位(缺省是空格)

8. w.d (两个整数用半角句号隔开)- 指定输出域宽及精度

b. "fillChar"是填空位符(缺省为空格)

--你可以用MyOut.fillChar = '*'或'$'来定义你自己的空位符

举例:

println(123.45678, "8.3L") -> 123.457(左对齐占八位)

println(123.45678, "10.3cs") -> 1.235E2 (居中占十位)

println(1234567, ",10") -> 1,234,567(右对齐占十位)

// class MyOut

import java.io.PrintStream;

import java.io.PrintWriter;

import java.io.OutputStreamWriter;

import java.text.DecimalFormat;

import java.text.NumberFormat;

/* Thanks to Prof. H.Roumani.(He is my java teacher, who is great.)

*

* The format methods receive the value to be formatted (which can

* be of any type) and a format descriptor: a string that contains

* one or more of the following flags in any order and in any case:

*

* L:

* By default, all values are aligned right within their field

* width. If this flag is specified, left alignment is used instead.

* This flag has no effect if the field width is not specified.

* C:

* By default, all values are aligned right within their field

* width. If this flag is specified, centre alignment is used instead.

* This flag has no effect if the field width is not specified.

* X:

* By default, all numeric values are shown in the decimal system.

* If this flag is specified, hexadecimal is used instead (showing

* IEEE-754 for real's). This flag has no effect if the value is not

* numeric.

* B:

* By default, all numeric values are shown in the decimal system.

* If this flag is specified, binary is used instead (showing

* IEEE-754 for real's). This flag has no effect if the value is not

* numeric.

* ,:

* By default, all numeric, base-10 values are shown without a

* thousand-separator. If this flag is specified, a comma is inserted

* in the integer part of the number to separate thousands. This flag

* has no effect if the value is not numeric, is not in decimal, or if

* the scientific notation is used.

* S:

* By default, all numeric, base-10 values are shown as an integer part

* followed by a mantissa, or fractional part. If this flag is specified,

* scientific notation is used: One digits (possibly preceded by a minus

* sign) followed by a decimal point, a mantissa, the letter 'E' and an

* eXPonent. This flag has no effect if the value is not numeric or is not

* in decimal.

* Z:

* By default, all integer, base-10 values are shown with leading or

* trailing spaces to fill the specified field width. If this flag is

* specified, the field is filled with leading zeros instead. This flag is

* only meaningful if the value is a base-10 integer, the width is specified,

* and the thousand-separator flag is not specified.

* w.d (two integers separated by a period):

* w is the desired width of the entire returned string, after formatting.

* If the formatted string is shorter than w, it will be padded by leading

* and/or trailing spaces (or some other fill character) depending on the

* requested alignment (left, right, or centre). d is the desired number of

* decimals and is meaningful only if the value is a base-10 real (in standard

* or scientific notation). Rounding to the specified number of decimals is

* done using conventional rules but the case of 5 is handled by rounding to

* the nearest even number (same as the rint method of the Math class). Note

* that you can specify only w (in that case don't include the period), or

* only d (in this last case do precede it by the period).

*/

 
 
 
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