Use setRoundingMode, set the RoundingMode explicitly to handle your issue with the half-even round, then use the format pattern for your required output.
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DecimalFormat df = new DecimalFormat("#.####"); df.setRoundingMode(RoundingMode.CEILING); for (Number n : Arrays.asList(12, 123.12345, 0.23, 0.1, 2341234.212431324)) { Double d = n.doubleValue(); System.out.println(df.format(d)); } |
gives the output:
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12 123.1235 0.23 0.1 2341234.2125 |
What I’d like is a method to convert a double to a string which rounds using the half-up method. I.e. if the decimal to be rounded is a 5, it always rounds up the previous number. This is the standard method of rounding most people expect in most situations.
I also would like only significant digits to be displayed. That is there should not be any trailing zeroes.
I know one method of doing this is to use the String.format method:
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String.format("%.5g%n",0.912385); |
returns:
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0.91239 |
which is great, however it always displays numbers with 5 decimal places even if they are not significant:
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String.format("%.5g%n",0.912300); |
returns:
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0.91230 |
Another method is to use the DecimalFormatter:
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DecimalFormat df = new DecimalFormat("#.#####"); df.format(0.912385); |
returns:
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0.91238 |
However as you can see this uses half-even rounding. That is it will round down if the previous digit is even. What I’d like is this:
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0.912385-0.91239 |
0.912300->0.9123