数字的格式化
2006-04-19 09:41 Jeff 阅读(1082) 评论(0) 编辑 收藏 举报
Java中数字格式的处理.主要是用到抽象类java.text.NumberFormat和它的子类java.text..DecimalFormat.具体的细节可以查看API文档,总结一下数字格式化的使用方法:
// The 0 symbol shows a digit or 0 if no digit present
NumberFormat formatter = new DecimalFormat("000000");
String s = formatter.format(-1234.567); // -001235
// notice that the number was rounded up
// The # symbol shows a digit or nothing if no digit present
formatter = new DecimalFormat("##");
s = formatter.format(-1234.567); // -1235
s = formatter.format(0); // 0
formatter = new DecimalFormat("##00");
s = formatter.format(0); // 00
// The . symbol indicates the decimal point
formatter = new DecimalFormat(".00");
s = formatter.format(-.567); // -.57
formatter = new DecimalFormat("0.00");
s = formatter.format(-.567); // -0.57
formatter = new DecimalFormat("#.#");
s = formatter.format(-1234.567); // -1234.6
formatter = new DecimalFormat("#.######");
s = formatter.format(-1234.567); // -1234.567
formatter = new DecimalFormat(".######");
s = formatter.format(-1234.567); // -1234.567
formatter = new DecimalFormat("#.000000");
s = formatter.format(-1234.567); // -1234.567000
// The , symbol is used to group numbers
formatter = new DecimalFormat("#,###,###");
s = formatter.format(-1234.567); // -1,235
s = formatter.format(-1234567.890); // -1,234,568
// The ; symbol is used to specify an alternate pattern for negative values
formatter = new DecimalFormat("#;(#)");
s = formatter.format(-1234.567); // (1235)
// The ' symbol is used to quote literal symbols
formatter = new DecimalFormat("'#'#");
s = formatter.format(-1234.567); // -#1235
formatter = new DecimalFormat("'abc'#");
s = formatter.format(-1234.567); // -abc1235
为了格式化当前语言环境的数字,要使用一个工厂类方法:
myString = NumberFormat.getInstance().format(myNumber);
要格式化不同语言环境的日期,可在 getInstance 的调用中指定它:
NumberFormat nf = NumberFormat.getInstance(Locale.FRENCH);
DecimalFormat
是 NumberFormat
的一个具体子类,用于格式化十进制数字。该类设计有各种功能,使其能够分析和格式化任意语言环境中的数,包括对西方语言、阿拉伯语和印度语数字的支持。它还支持不同类型的数,包括整数 (123)、定点数 (123.4)、科学记数法表示的数 (1.23E4)、百分数 (12%) 和金额 ($123)。所有这些内容都可以本地化。
要获取具体语言环境的 NumberFormat
(包括默认语言环境),可调用 NumberFormat
的某个工厂方法,如 getInstance()
。通常不直接调用 DecimalFormat
的构造方法,因为 NumberFormat
的工厂方法可能返回不同于 DecimalFormat
的子类。如果需要自定义格式对象,可执行:
NumberFormat f = NumberFormat.getInstance(loc);
if (f instanceof DecimalFormat) {
((DecimalFormat) f).setDecimalSeparatorAlwaysShown(true);
}
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。下面是一些模式运用的例子:
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