OCJP之国际化 更新中

介绍几个java.text.*包下的类

1. NumberFormat

    1.1 作用

    取当前系统的数字格式，比如货币

    1.2 实例化

    NumberFormat.getInstance();

    1.3 常用方法

    NumberFormat.parse(String str)

    -- 返值为: String

    -- 异常必须处理，否则报编译错误, Exception occurs when first char cannot be parsed;

    -- 参数里不是每个字符都用得上，当遇到字符时，无法转成数字，参数就提取到non-numberic char

    NumberFormat.format(long number);

    -- 返值为: Number

    -- 异常为runtime Exception，当参数为非数字时，运行时抛IllegalArgumentException，编译可以通过

    1.4 代码实例

package com.ocjp.g11n;import java.text.NumberFormat;import java.text.ParseException;import java.util.Locale;public class TestNumberFormat {public static void main(String[] args) {new TestNumberFormat().go();} public void go() { NumberFormat nf, nf2; Number n; Locale[] la = NumberFormat.getAvailableLocales(); for(int x=0; x < 10; x++) { nf = NumberFormat.getCurrencyInstance(la[x]); System.out.println(nf.format(123.456f)); } nf2 = NumberFormat.getInstance(); try { //exception must be handled or declared; if the first char cannot be parsed, it will throw out ParseException; //NumberFormat.parse() will return Number, pay attention that not fully String will be used, for this case, f will be discarded; //not all String will be used,n = nf2.parse("123.456f");} catch (ParseException e) {// TODO Auto-generated catch blocke.printStackTrace();}  //NumberFormat.fortmat(long number); the parameter must be Number; it returns String; //IllegalArugmentException(Runtime Exception, not checked at compiling time) will be thrown out at running time if pass an non-Number parameter; // System.out.println(nf2.format("123.456")); System.out.println(nf2.format(123.456)); }}

//Output

RM123.46
ر.ق.‏ 123.46
123, kr.
123,46 €
¤ 123,46
€123.46
SFr. 123.46
123,46 €
ر.س.‏ 123.46
د.ع.‏ 123.456
123.456

2 Calendar

月份的范围是0-11，也就是说0代表1月

常用方法:

Calendar.add(); 既改变大的字段，又改变小的字段

Calendar.roll(); 只改变小的字段

代码一：

import java.util.*;public class Wise {public static void main(String[] args) {Calendar c = Calendar.getInstance();c.set(1999,11,25); //MONTH is [0-11]; This is Dec.25th, 1999;//roll() doesn't change the bigger field(YEAR in this case); only change smaller field(DAY in this case);c.roll(Calendar.MONTH, 3);System.out.println(c.getTime()); //Output is Mar. 25th, 1999;//add() will change both bigger and smaller field;c.add(Calendar.DATE, 10);System.out.println(c.getTime());} }

Output:

Thu Mar 25 13:57:07 EST 1999
Sun Apr 04 13:57:07 EDT 1999

代码二：

package com.ocjp.g11n;import java.util.*;public class CalendarTest { public static void main(String[] args) { Calendar c = Calendar.getInstance(); c.set(1999,8,31); //MONTH是从0-11；所以这里实际上是指1999年9月31日，因为9月没有31日，实际上就转成了1999年10月1日； System.out.println(c.getTime()); c.roll(Calendar.MONTH, 11); System.out.println(c.getTime()); c.add(Calendar.DATE, 10); System.out.println(c.getTime()); }}

Output:

Fri Oct 01 14:03:05 EDT 1999
Wed Sep 01 14:03:05 EDT 1999
Sat Sep 11 14:03:05 EDT 1999