1. Create an object of java.text.DecimalFormat with pattern as empty string.
2. maximumFractionDigits is initialized to Integer.MAX_VALUE by default.
3. Use this DecimalFormat object in BigDecimal.setScale like:
BigDecimal rounded = number.setScale(decimalFormat.getMaximumFractionDigits(), 4);
4. It leads to an exception -
java.lang.NegativeArraySizeException
at java.math.BigDecimal.tenToThe(BigDecimal.java:2839)
at java.math.BigDecimal.setScale(BigDecimal.java:2047)
5. This happens because setScale() method tries to create a char array with size (n + 1). In this case, 'n' is Integer.MAX_VALUE; so adding 1 to it makes it negative which causes this exception.
6. In Java 1.4, maximumFractionDigits was initialized to 340; in that case above exception would not have come up. It imples that there is some backward compatibility issue.


DecimalFormatSymbols syms = new DecimalFormatSymbols();
syms.setDecimalSeparator('.');
syms.setGroupingSeparator(',');
DecimalFormat decimalFormat = new DecimalFormat("", syms);
BigDecimal number = new BigDecimal(363.0);
BigDecimal rounded = number.setScale(decimalFormat.getMaximumFractionDigits(), 4);