考虑到您的建议,我稍微修改了我的代码以涵盖不同的本地化信息。关键是将以本地化格式表示的值字符串转换为基于格式字符串进行舍入的Double类型。
格式字符串始终基于英国格式,小数分隔符为“.”,千位分隔符为“,”。
我使用DecimalFormat来解析指定区域设置的本地化格式。这样可以正确获得字符串的Double等效项。然后我使用BigDecimal来处理舍入。我可以从DecimalFormat实例获取小数位数,然后调用setScale方法对BigDecimal进行舍入操作。
初始代码结构已经修改,以便您可以查看在不同语言环境下发生的情况。感谢@RD01指出其他语言环境的重要性。
现在我的代码如下:
private void runTests3() {
System.out.println( "Current Locale is " + Locale.getDefault().toString() );
String numbersInEuropeanFormatString[] = new String[] { "1.000,234567", "1,2345678", "1.222.333,234567" };
String formatUK = "###,##0.0000";
System.out.println("Output numbers using the German locale\n");
for(String num : numbersInEuropeanFormatString ) {
formatNumberAsDouble(num, formatUK, Locale.GERMAN);
}
System.out.println("Output numbers using the UK locale\n");
for(String num : numbersInEuropeanFormatString ) {
formatNumberAsDouble(num, formatUK, Locale.UK);
}
System.out.println("\n\nOutput numbers using new DecimalFormat( " + formatUK + " )\n");
for(String num : numbersInEuropeanFormatString ) {
formatNumberAsDouble( num, formatUK, null);
}
}
private void formatNumberAsDouble(String value, String format, Locale locale) {
NumberFormat formatter;
int decimalPlaces;
if( locale != null ) {
formatter = NumberFormat.getNumberInstance(locale);
decimalPlaces = (new DecimalFormat(format)).getMaximumFractionDigits();
} else {
formatter = new DecimalFormat( format );
decimalPlaces = formatter.getMaximumFractionDigits();
}
Double result = null;
try {
result = formatter.parse( value ).doubleValue();
} catch( ParseException ex ) {
}
BigDecimal bd = new BigDecimal(result );
Double roundedValue = bd.setScale( decimalPlaces, RoundingMode.HALF_UP ).doubleValue();
System.out.println("\tValue = " + value);
System.out.println( locale == null ? "\tLocale not specified" : "\tLocale = " + locale.toString());
System.out.println( format == null || format.length() == 0 ? "\tFormat = Not specified" : "\tFormat = " + format);
System.out.println("\tResult (Double) = " + result);
System.out.println("\tRounded Result (Double) (" + decimalPlaces + "dp) = " + roundedValue);
System.out.println("");
}
这将产生以下输出:
Current Locale is nl_BE
Output numbers using the German locale
Value = 1.000,234567
Locale = de
Format = ###,##0.0000
Result (Double) = 1000.234567
Rounded Result (Double) (4dp) = 1000.2346
Value = 1,2345678
Locale = de
Format = ###,##0.0000
Result (Double) = 1.2345678
Rounded Result (Double) (4dp) = 1.2346
Value = 1.222.333,234567
Locale = de
Format = ###,##0.0000
Result (Double) = 1222333.234567
Rounded Result (Double) (4dp) = 1222333.2346
Output numbers using the UK locale
Value = 1.000,234567
Locale = en_GB
Format = ###,##0.0000
Result (Double) = 1.0
Rounded Result (Double) (4dp) = 1.0
Value = 1,2345678
Locale = en_GB
Format = ###,##0.0000
Result (Double) = 1.2345678E7
Rounded Result (Double) (4dp) = 1.2345678E7
Value = 1.222.333,234567
Locale = en_GB
Format = ###,##0.0000
Result (Double) = 1.222
Rounded Result (Double) (4dp) = 1.222
Output numbers using new DecimalFormat( ###,##0.0000 )
Value = 1.000,234567
Locale not specified
Format = ###,##0.0000
Result (Double) = 1000.234567
Rounded Result (Double) (4dp) = 1000.2346
Value = 1,2345678
Locale not specified
Format = ###,##0.0000
Result (Double) = 1.2345678
Rounded Result (Double) (4dp) = 1.2346
Value = 1.222.333,234567
Locale not specified
Format = ###,##0.0000
Result (Double) = 1222333.234567
Rounded Result (Double) (4dp) = 1222333.2346