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分享：java中的格式化输出（类似C语言的printf） [复制链接]

小飞爱使申华

小富即安

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电梯直达

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发表于 2003-08-09 11:04 |只看该作者 |倒序浏览

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).
*/
public class MyOut
{
/*************************************************************
Formats the passed value using the passed format descriptor
and returns the result as a string.
@param value the value to be formatted.
@param fd the format descriptor.
@return the formatted value as a string.
**************************************************************/
public static String format(byte value, String fd)
{
return formatInteger(value, fd, 8);
}
/*************************************************************
Formats the passed value using the passed format descriptor
and returns the result as a string.
@param value the value to be formatted.
@param fd the format descriptor.
@return the formatted value as a string.
**************************************************************/
public static String format(char value, String fd)
{
return formatInteger(value, fd, 16);
}
/*************************************************************
Formats the passed value using the passed format descriptor
and returns the result as a string.
@param value the value to be formatted.
@param fd the format descriptor.
@return the formatted value as a string.
**************************************************************/
public static String format(double value, String fd)
{
extractAttributes(fd);
String s1;
if(base == 'B')
{
s1 = Long.toBinaryString(Double.doubleToLongBits(value));
s1 = repeat(64, '0') + s1;
s1 = s1.substring(s1.length() - 64);
} else if(base == 'X')
{
s1 = Long.toHexString(Double.doubleToLongBits(value));
s1 = repeat(16, '0') + s1;
s1 = s1.substring(s1.length() - 16);
} else
{
pattern = decimals != -1 ? "." + repeat(decimals, '0') : ".#";
if(scientific)
pattern = "0" + pattern + "E0";
else
pattern = separator ? "#,##0" + pattern : "0" + pattern;
s1 = (new DecimalFormat(pattern)).format(value);
}
return size(s1);
}
/*************************************************************
Formats the passed value using the passed format descriptor
and returns the result as a string.
@param value the value to be formatted.
@param fd the format descriptor.
@return the formatted value as a string.
**************************************************************/
public static String format(float value, String fd)
{
extractAttributes(fd);
String s1;
if(base == 'B')
{
s1 = Integer.toBinaryString(Float.floatToIntBits(value));
s1 = repeat(32, '0') + s1;
s1 = s1.substring(s1.length() - 32);
} else if(base == 'X')
{
s1 = Integer.toHexString(Float.floatToIntBits(value));
s1 = repeat(8, '0') + s1;
s1 = s1.substring(s1.length() - 8);
} else
{
pattern = decimals != -1 ? "." + repeat(decimals, '0') : ".#";
if(scientific)
pattern = "0" + pattern + "E0";
else
pattern = separator ? "#,##0" + pattern : "0" + pattern;
s1 = (new DecimalFormat(pattern)).format(value);
}
return size(s1);
}
/*************************************************************
Formats the passed value using the passed format descriptor
and returns the result as a string.
@param value the value to be formatted.
@param fd the format descriptor.
@return the formatted value as a string.
**************************************************************/
public static String format(int value, String fd)
{
return formatInteger(value, fd, 32);
}
/*************************************************************
Formats the passed value using the passed format descriptor
and returns the result as a string.
@param value the value to be formatted.
@param fd the format descriptor.
@return the formatted value as a string.
**************************************************************/
public static String format(long value, String fd)
{
return formatInteger(value, fd, 64);
}
/*************************************************************
Formats the passed value using the passed format descriptor
and returns the result as a string.
@param value the value to be formatted.
@param fd the format descriptor.
@return the formatted value as a string.
**************************************************************/
public static String format(short value, String fd)
{
return formatInteger(value, fd, 16);
}
/* Formats the passed value using the passed format descriptor
* and returns the result as a string.
*/
private static String formatInteger(long l, String s, int i)
{
extractAttributes(s);
String s1;
if(base == 'B')
{
s1 = Long.toBinaryString(l);
s1 = repeat(64, '0') + s1;
s1 = s1.substring(s1.length() - i);
} else
if(base == 'X')
{
s1 = Long.toHexString(l);
s1 = repeat(16, '0') + s1;
s1 = s1.substring(s1.length() - i / 4);
} else
if(separator)
{
s1 = (new DecimalFormat("#,###")).format(l);
} else
{
s1 = String.valueOf(l);
if(zeroFill)
s1 = repeat(width - s1.length(), '0') + s1;
}
return size(s1);
}
// Gets information from the passed format descriptor.
private static void extractAttributes(String s)
{
s = s.toUpperCase();
alignment = 'R';
separator = false;
base = 'D';
scientific = false;
zeroFill = false;
width = -1;
decimals = -1;
int i = s.indexOf(76, 0);
if(i >; -1)
{
alignment = 'L';
s = s.substring(0, i) + s.substring(i + 1);
}
i = s.indexOf(67, 0);
if(i >; -1)
{
alignment = 'C';
s = s.substring(0, i) + s.substring(i + 1);
}
i = s.indexOf(44, 0);
if(i >; -1)
{
separator = true;
pattern = pattern + ",###";
s = s.substring(0, i) + s.substring(i + 1);
}
i = s.indexOf(88, 0);
if(i >; -1)
{
base = 'X';
s = s.substring(0, i) + s.substring(i + 1);
} else
{
i = s.indexOf(66, 0);
if(i >; -1)
{
base = 'B';
s = s.substring(0, i) + s.substring(i + 1);
}
}
i = s.indexOf(83, 0);
if(i >; -1)
{
scientific = true;
s = s.substring(0, i) + s.substring(i + 1);
}
i = s.indexOf(90, 0);
if(i >; -1)
{
zeroFill = true;
s = s.substring(0, i) + s.substring(i + 1);
}
i = s.indexOf(46, 0);
if(i >; -1)
{
decimals = Integer.parseInt(s.substring(i + 1));
s = s.substring(0, i);
}
if(s.length() >; 0)
width = Integer.parseInt(s);
}
/*************************************************************
Output the passed value to the standard output device using
the passed format descriptor. No trailing End-Of-Line
character is printed.
@param value the value to be printed.
@param fd the format descriptor.
**************************************************************/
public static void print(byte value, String fd)
{
handle.print(format(value, fd));
handle.flush();
}
/*************************************************************
Output the passed value to the standard output device using
the passed format descriptor. No trailing End-Of-Line
character is printed.
@param value the value to be printed.
@param fd the format descriptor.
**************************************************************/
public static void print(char value, String fd)
{
handle.print(format(value, fd));
handle.flush();
}
/*************************************************************
Output the passed value to the standard output device using
the passed format descriptor. No trailing End-Of-Line
character is printed.
@param value the value to be printed.
@param fd the format descriptor.
**************************************************************/
public static void print(double value, String fd)
{
handle.print(format(value, fd));
handle.flush();
}
/*************************************************************
Output the passed value to the standard output device using
the passed format descriptor. No trailing End-Of-Line
character is printed.
@param value the value to be printed.
@param fd the format descriptor.
**************************************************************/
public static void print(float value, String fd)
{
handle.print(format(value, fd));
handle.flush();
}
/*************************************************************
Output the passed value to the standard output device using
the passed format descriptor. No trailing End-Of-Line
character is printed.
@param value the value to be printed.
@param fd the format descriptor.
**************************************************************/
public static void print(int value, String fd)
{
handle.print(format(value, fd));
handle.flush();
}
/*************************************************************
Output the passed value to the standard output device using
the passed format descriptor. No trailing End-Of-Line
character is printed.
@param value the value to be printed.
@param fd the format descriptor.
**************************************************************/
public static void print(long value, String fd)
{
handle.print(format(value, fd));
handle.flush();
}
/*************************************************************
Output the passed value to the standard output device using
the passed format descriptor. No trailing End-Of-Line
character is printed.
@param value the value to be printed.
@param fd the format descriptor.
**************************************************************/
public static void print(short value, String fd)
{
handle.print(format(value, fd));
handle.flush();
}
/*************************************************************
Output the passed value to the standard output device using
the passed format descriptorand followed by an End-Of-Line
marker.
@param value the value to be printed.
@param fd the format descriptor.
**************************************************************/
public static void println(byte value, String fd)
{
print(value, fd);
handle.print(EOL);
handle.flush();
}
/*************************************************************
Output the passed value to the standard output device using
the passed format descriptorand followed by an End-Of-Line
marker.
@param value the value to be printed.
@param fd the format descriptor.
**************************************************************/
public static void println(char value, String fd)
{
print(value, fd);
handle.print(EOL);
handle.flush();
}
/*************************************************************
Output the passed value to the standard output device using
the passed format descriptorand followed by an End-Of-Line
marker.
@param value the value to be printed.
@param fd the format descriptor.
**************************************************************/
public static void println(double value, String fd)
{
print(value, fd);
handle.print(EOL);
handle.flush();
}
/*************************************************************
Output the passed value to the standard output device using
the passed format descriptorand followed by an End-Of-Line
marker.
@param value the value to be printed.
@param fd the format descriptor.
**************************************************************/
public static void println(float value, String fd)
{
print(value, fd);
handle.print(EOL);
handle.flush();
}
/*************************************************************
Output the passed value to the standard output device using
the passed format descriptorand followed by an End-Of-Line
marker.
@param value the value to be printed.
@param fd the format descriptor.
**************************************************************/
public static void println(int value, String fd)
{
print(value, fd);
handle.print(EOL);
handle.flush();
}
/*************************************************************
Output the passed value to the standard output device using
the passed format descriptorand followed by an End-Of-Line
marker.
@param value the value to be printed.
@param fd the format descriptor.
**************************************************************/
public static void println(long value, String fd)
{
print(value, fd);
handle.print(EOL);
handle.flush();
}
/*************************************************************
Output the passed value to the standard output device using
the passed format descriptorand followed by an End-Of-Line
marker.
@param value the value to be printed.
@param fd the format descriptor.
**************************************************************/
public static void println(short value, String fd)
{
print(value, fd);
handle.print(EOL);
handle.flush();
}
// Returns the string padding with 'fillChar'.
private static String size(String s)
{
int i = width - s.length();
if(alignment == 'R')
return repeat(i, fillChar) + s;
if(alignment == 'L')
return s + repeat(i, fillChar);
else
return repeat(i / 2, fillChar) + s + repeat(i / 2 + i % 2, fillChar);
}
// Repeats the passed character 'times' times.
public static String repeat(int times, char c)
{
String s = "";
for(int i = 0; i < times; i++)
s = s + c;
return s;
}
private static final String EOL = System.getProperty("line.separator");
private static PrintWriter handle = new PrintWriter(new OutputStreamWriter(System.out));
public static char fillChar = ' ';
private static char alignment;
private static boolean separator;
private static char base;
private static boolean scientific;
private static boolean zeroFill;
private static int width;
private static int decimals;
private static String pattern;
}