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Editorial Team
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Asked: 2026-06-01T21:15:00+00:00

Let’s look at the following statements in Java. System.out.println(new DecimalFormat(0).format(2.4)); //returns 2 System.out.println(new DecimalFormat(0).format(2.5));

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Let’s look at the following statements in Java.

System.out.println(new DecimalFormat("0").format(2.4)); //returns 2

System.out.println(new DecimalFormat("0").format(2.5)); //returns 2  <---Concentrate here
System.out.println(Math.round(2.5));                    //returns 3

System.out.println(new DecimalFormat("0").format(2.6)); //returns 3
System.out.println(new DecimalFormat("0").format(3.5)); //returns 4

In the above statements, all other cases are obvious except the following.

System.out.println(new DecimalFormat("0").format(2.5));

It should return 3 but it returns 2. How?

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1 Answer

  1. Editorial Team

    This is intentional behavior. From the documentation:

    Rounding

    DecimalFormat uses half-even rounding (see ROUND_HALF_EVEN) for formatting.

    About ROUND_HALF_EVEN:

    Rounding mode to round towards the "nearest neighbor" unless both neighbors are equidistant, in which case, round towards the even neighbor. Behaves as for ROUND_HALF_UP if the digit to the left of the discarded fraction is odd; behaves as for ROUND_HALF_DOWN if it’s even. Note that this is the rounding mode that minimizes cumulative error when applied repeatedly over a sequence of calculations.

    This is also known as banker’s rounding.

    Math.Round on the other hand uses the following formula, which is "normal" rounding:

    (long)Math.floor(a + 0.5d)
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