The round(num, decimalPlaces) function doesn't work on locales that use comma as the decimal separator.

[mdudzinski]

Software versions

JavaRosa since 7d0e596 (PR #33 , Issue #5).

Problem description

The round(num, decimalPlaces) function doesn't work on locales that use comma as the decimal mark (Polish Locale for example:)).

Steps to reproduce the problem

I reproduced this problem by running the test suite on my machine which has PL locale.
The suite crashes with the following information:

java.lang.NumberFormatException: For input string: "14,3"
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2043)
at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
at java.lang.Double.parseDouble(Double.java:538)
at java.lang.Double.valueOf(Double.java:502)
at org.javarosa.xpath.expr.XPathFuncExpr.round(XPathFuncExpr.java:1055)
at org.javarosa.xpath.expr.XPathFuncExpr.eval(XPathFuncExpr.java:200)
at org.javarosa.xpath.test.XPathEvalTest.testEval(XPathEvalTest.java:86)
at org.javarosa.xpath.test.XPathEvalTest.testEval(XPathEvalTest.java:65)
at org.javarosa.xpath.test.XPathEvalTest.doTests(XPathEvalTest.java:322)

This comes from test for "round('14.29123456789', 1)" expression but I checked and the suite will fall for any round expression that have more than 0 as the power parameter.

Expected behavior

The test just passes.

Other information

The following code causes this behaviour:

            final NumberFormat nf = NumberFormat.getNumberInstance();
            nf.setMaximumFractionDigits(numDecimals);
            nf.setGroupingUsed(false);
            return Double.valueOf(nf.format(number));

It uses NumberFormat's capabilities to round a decimal number. It works great but this class follows the current locale settings and produces a readable string that matches the locale's rules. The result is later passed to Double.valueOf which doesn't handle comma as the decimal separator.

For example, in Poland nf.format(number) for number=14.29123456789 and numDecimals=1 will return 14,3 instead of 14.3.