Java字符串+日期+数字格式化输出.docx

1、Java字符串+日期+数字格式化输出Java字符串日期数字格式化输出在C中可以使用类似printf(“%d %8.2fn”, 1001, 52.335的方法实现格式化输出,可是Java中的System.out.println(并没有对应的功能。要格式化输出,必须使用java.text包中的类来实现类似的操作(要不怎么体现面向对象的优越性呢,不过据说jdk1.5准备又补上。当然了,java.text包的功能还是很强大的,奇怪的是很多书中都没有涉及,而一般谁又有工夫整天去看API?注意:由于这里说得很简略,因此请参照下面的Demo程序。格式化数字在NumberFormat类中为我们提供了格式化4种

2、数字的方法:整数、小数、货币和百分比,通过工厂方法getNumberInstance, getNumberIntance, getCurrencyInstance, getPercentInstance方法获得相应的实例对象就行。例如我们要以字符串表示人民币88888.88元,这样来写就行:NumberFormat nf = NumberFormat.getCurrencyInstance(;System.out.println(nf.format(88888.88;定制格式化数字可是对于稍微复杂一点的需求,NumberFormat就满足不了了,幸好java还提供了DecimalFormat实

3、现定制的格式化。要使用DecimalFormat对象,必须提供给它提供一个格式化的模式(pattern:String pattern = DecimalFormat df = new DecimalFormat(pattern;或者:DecimalFormat df = new DecimalFormat(;df. applyPattern(pattern;然后就调用它的format方法就行了。所以关键就是这个模式怎么定义。在DecimalFormat类的Java Doc中有模式的语法表示,不过很难说清楚(是我说不清楚,呵呵,请看看Demo自己多试试吧。下面是模式中某些字符的含义表:字符含义一

4、位数字,这一位缺失显示为0。用来补零#一位数字, 这一位缺失就不显示.小数点,不用多说了吧,千位分隔符E科学计数法%百分比格式化日期把日期转化为字符串最简单的方法就是调用Date类的toString或者toLocaleString方法:System.out.println(new Date(;输出:2004-8-7 8:16:14。可是如果我们想把月和日补成2位不要时分秒2004-08-07,这就不灵了。java.text.DateFormat提供了大量的工厂方法: getDateInstance(int style, getTimeInstance(int style, getDateTim

5、eInstance(int dateStyle, int timeStyle等等。其中style必须是DateFormat.LONG, DateFormat.MEDIUM, DateFormat.SHORT之一。Demo中的defaultDateFormat方法作了一个简单的实验。定制格式化日期:同样,java.text.SimpleDateFormat可以通过模式(pattern实现定制格式化:String pattern = SimpleDateFormat df = new SimpleDateFormat(pattern;或者:SimpleDateFormat df = new Sim

6、pleDateFormat(;df. applyPattern(pattern;下面是SimpleDateFormat的javadoc中的一个模式符号简表:符号意义合法数值示例yYearYear1996; 96MMonth in yearMonthJuly; Jul; 07d PageDay in monthNumber10aAm/pm markerTextPMHHour in day (0-23NumberhHour in am/pm (1-12Number12mMinute in hourNumber30sSecond in minuteNumber55SMillisecondNumber

7、978zTime zoneGeneral time zonePacific Standard Time; PST; GMT-08:00ZTime zoneRFC 822 time zone-0800注意的是,符号的大小写意义是不同的,符号的个数也会导致输出不一样。例如用MM就会把1月份显示成01,而用M则不会补零。对于年份,两个yy会只输出两位年份,yyyy则会输出4位年份。实际上,上面的类还提供了很多其他方法,特别是用于本地化(Locale定制格式化的方法,以及从字符串表示转化为相应对象的parse方法,还有把格式化结果附加到一个StringBuffer的方法(应该是用来提高性能。最后是一个

8、小Demo和输出结果:TestFormat.java:import java.text.*;import java.util.*;public class TestFormat public static void main(String args defaultNumberFormat(;System.out.println(;customNumberFormat(;System.out.println(;defaultDateFormat(;System.out.println(;customDateFormat(;System.out.println(;public static voi

9、d defaultNumberFormat( int i = 123456;double x = 882323.23523;double p = 0.528;double c = 52.83; PageNumberFormat nf = NumberFormat.getInstance(;System.out.println(Integer + i + is displayed as + nf.format(i;System.out.println(Double + x + is displayed as + nf.format(x;NumberFormat nfInt = NumberFor

10、mat.getIntegerInstance(;System.out.println(Integer + i + is displayed as + nfInt.format(i;NumberFormat nfNumber = NumberFormat.getNumberInstance(;System.out.println(Double + x + is displayed as + nfNumber.format(x;NumberFormat nfPercent = NumberFormat.getPercentInstance(;System.out.println(Percent +

11、 p + is displayed as + nfPercent.format(p;NumberFormat nfCurrency = NumberFormat.getCurrencyInstance(;System.out.println(Currency + p + is displayed as + nfCurrency.format(c;/这里没有涉及相应的parse方法public static void customNumberFormat( double x = 1000.0 / 3;System.out.println(default output is + x;pattern

12、Print(#,#.#, x;patternPrint(#.#, x;patternPrint(#.00, x;patternPrint(#.0#, x; PagepatternPrint(00000.#, x;patternPrint($#,#.#, x;patternPrint(0.#E0, x;patternPrint(00.#%, x;double y = 23.0012;System.out.println(default output is + y;patternPrint(#,#.#, y;patternPrint(#.#, y;patternPrint(#.00, y;patt

13、ernPrint(#.0#, y;patternPrint(00000.#, y;patternPrint($#,#.#, y;patternPrint(0.#E0, y;patternPrint(00.#%, y;public static void patternPrint(String pattern, double x DecimalFormat df = new DecimalFormat(pattern;System.out.println(output for pattern + pattern + is + df.format(x;public static void defa

14、ultDateFormat(Date date = new Date(;System.out.println(simple date +date.toLocaleString(;DateFormat df = DateFormat.getDateTimeInstance(;System.out.println(df.format(date;DateFormat dfLong =DateFormat.getDateTimeInstance(DateFormat.LONG, DateFormat.LONG; System.out.println(dfLong.format(date;DateFor

15、mat dfMedium =DateFormat.getDateTimeInstance(DateFormat.MEDIUM, PageDateFormat.MEDIUM;System.out.println(dfMedium.format(date;DateFormat dfShort =DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.SHORT; System.out.println(dfShort.format(date;public static void customDateFormat( Date date =

16、 new Date(;patternPrint(yyyy.MM.dd HH:mm:ss z, date; /两个MM, dd会导致补零patternPrint(yy年M月d日 HH时mm分, date; /两个yy 就显示为两位年份patternPrint(EEE, MMM d, yy, date;patternPrint(h:mm a, date;patternPrint(hh oclock a, zzzz, date;patternPrint(yyyyy.MMMMM.dd GGG hh:mm aaa, date;patternPrint(EEE, d MMM yyyy HH:mm:ss Z

17、, date;patternPrint(yyMMddHHmmssZ, date;public static void patternPrint(String pattern, Date dateSimpleDateFormat df = new SimpleDateFormat(pattern;System.out.println(df.format(date;输出:Integer 123456 is displayed as 123,456Double 882323.23523 is displayed as 882,323.235Integer 123456 is displayed as

18、 123,456Double 882323.23523 is displayed as 882,323.235Percent 0.528 is displayed as 53%Currency 0.528 is displayed as ￥52.83default output is 333.3333333333333output for pattern #,#.# is 333.33output for pattern #.# is 333.33 Page output for pattern #.00 is 333.33output for pattern #.0# is 333.33ou

19、tput for pattern 00000.# is 00333.33output for pattern $#,#.# is $333.33 output for pattern 0.#E0 is 3.333E2output for pattern 00.#% is 33333.33%default output is 23.0012output for pattern #,#.# is 23output for pattern #.# is 23output for pattern #.00 is 23.00output for pattern #.0# is 23.0output fo

20、r pattern 00000.# is 00023output for pattern $#,#.# is $23output for pattern 0.#E0 is 2.3E1output for pattern 00.#% is 2300.12%simple date 2004-8-7 8:16:142004-8-7 8:16:142004年8月7日上午08时16分14秒2004-8-7 8:16:14 04-8-7 上午 8:16 2004.08.07 08:16:14 GMT+08:00 04 年 8 月 7 日 08 时 16 分 星期六, 八月 7, 04 8:16 上午 08 oclock 上午, GMT+08:00 02004.八月.07 公元 08:16 上午 星期六, 7 八月 2004 08:16:14 +0800 040807081614+0800