Unpredicatable rounding decimals using Number Format/ Decimal Format

[Aparna Reguri]

Hi All,

The below code is used to round upto two digits after decimal.
1.215 is rounded to 1.22(correct)
1.225 is rounded to 1.22(incorrect)
1.235 is rounded to 1.24(correct)
1.245 is rounded to 1.24(incorrect)

    public static void main(String[] args) {
		  String str[] = {"1.215","1.225","1.235","1.245"};
		  
		  try
		  {
			  for(int i= 0 ; i<str.length ; i++)
			  {				  
				  double num = Double.parseDouble(str[i]);
				  DecimalFormat format = new DecimalFormat();
				  format.setMaximumFractionDigits(2);
				  format.setMinimumFractionDigits(2);	

				  DecimalFormat nformat = new DecimalFormat();
				  nformat.setMaximumFractionDigits(2);
				  nformat.setMinimumFractionDigits(2);				  

				  System.out.println("***"+ str[i]+"***");
				  System.out.println("Rounding using Decimal Formatting:"+format.format(num));
				  System.out.println("Rounding using Number Formatting:"+nformat.format(num));
			  }
		  }
		  catch(Exception e)
		  {
			  System.out.print("++"+e);
		  }
		
	}

Output:
***1.215***
Rounding using Decimal Formatting:1.22
Rounding using Number Formatting:1.22
***1.225***
Rounding using Decimal Formatting:1.22
Rounding using Number Formatting:1.22
***1.235***
Rounding using Decimal Formatting:1.24
Rounding using Number Formatting:1.24
***1.245***
Rounding using Decimal Formatting:1.24
Rounding using Number Formatting:1.24

Please let me know the behavior of formatting .
Thanks in Advance.

Cheers
>

[Christophe Verré]

If you take a look at the DecimalFormat API, you'll see that is uses BigDecimal#ROUND_HALF_EVEN to do the rounding. Check what ROUND_HALF_EVEN means, and everything's going to be clear, and predictable.

[Aparna Reguri]

It worked
Thanks a lot