在没有DecimalFormat的Java中使用模式解析数字

Question

Is there a Java parsing library similar to DecimalFormat ? I am unable to do what I want with DecimalFormat and regular expressions.

I need to be able to:

• Parse only an integer (DecimalFormat needs more settings than just pattern)
• Parse decimal (precise no rounding)
• Parse numbers like 123,456.789. (DecimalFormat for ###,###.### accepts "123456789" as well)

Answer 1

You could try treating it like a String and tokenizing it.

str.split("\\\\.") will split out the decimal side and then substring it to your precision, then on the number side you could split(",")

This is quite a bit of manual parsing work though...

Answer 2

I would use Regexp and NumberFormat :

Map<Pattern,NumberFormat> POSSIBLE_FORMATS = ...;
String input = ...;
Number value = null;
for (Map.Entry<Pattern,NumberFormat> possible : POSSIBLE_FORMATS.entrySet()) {
  if (possible.getKey().matcher(input).matches()) {
    value = possible.getKeValue().parse(input);
    break;
  }
}
if (value == null) {
  throw new IllegalArgumentExcption("no valid input format: " + input);
}