Rounding
Specifies a rounding behavior for numerical operations capable of discarding precision. Each rounding mode indicates how the least significant returned digit of a rounded result is to be calculated. If fewer digits are returned than the digits needed to represent the exact numerical result, the discarded digits will be referred to as the discarded fraction regardless the digits' contribution to the value of the number. In other words, considered as a numerical value, the discarded fraction could have an absolute value greater than one.
Each rounding mode description includes a table listing how different two-digit decimal values would round to a one digit decimal value under the rounding mode in question. The result column in the tables could be gotten by creating a BigDecimal number with the specified value, forming a MathContext object with the proper settings (precision set to 1, and the roundingMode set to the rounding mode in question), and calling round on this number with the proper MathContext. A summary table showing the results of these rounding operations for all rounding modes appears below.
| Input Number | Result of rounding input to one digit with the given rounding mode | |||||||
|---|---|---|---|---|---|---|---|---|
| `UP` | `DOWN` | `CEILING` | `FLOOR` | `HALF_UP` | `HALF_DOWN` | `HALF_EVEN` | `UNNECESSARY` | |
| 5.5 | 6 | 5 | 6 | 5 | 6 | 5 | 6 | throw `ArithmeticException` |
| 2.5 | 3 | 2 | 3 | 2 | 3 | 2 | 2 | throw `ArithmeticException` |
| 1.6 | 2 | 1 | 2 | 1 | 2 | 2 | 2 | throw `ArithmeticException` |
| 1.1 | 2 | 1 | 2 | 1 | 1 | 1 | 1 | throw `ArithmeticException` |
| 1.0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| -1.0 | -1 | -1 | -1 | -1 | -1 | -1 | -1 | -1 |
| -1.1 | -2 | -1 | -1 | -2 | -1 | -1 | -1 | throw `ArithmeticException` |
| -1.6 | -2 | -1 | -1 | -2 | -2 | -2 | -2 | throw `ArithmeticException` |
| -2.5 | -3 | -2 | -2 | -3 | -3 | -2 | -2 | throw `ArithmeticException` |
| -5.5 | -6 | -5 | -5 | -6 | -6 | -5 | -6 | throw `ArithmeticException` |
This enum is intended to replace the integer-based enumeration of rounding mode constants in BigDecimal (BigDecimal.ROUND_UP, BigDecimal.ROUND_DOWN, etc. ).
Author
Josh Bloch
Mike Cowlishaw
Joseph D. Darcy
Since
1.5
See also
Entries
Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round up. Behaves as for RoundingMode.UP if the discarded fraction is 0.5; otherwise, behaves as for RoundingMode.DOWN. Note that this is the rounding mode commonly taught at school.
Rounding mode to round towards the "nearest neighbor" unless both neighbors are equidistant, in which case, round towards the even neighbor. Behaves as for RoundingMode.HALF_UP if the digit to the left of the discarded fraction is odd; behaves as for RoundingMode.HALF_DOWN if it's even. Note that this is the rounding mode that statistically minimizes cumulative error when applied repeatedly over a sequence of calculations. It is sometimes known as "Banker's rounding," and is chiefly used in the USA. This rounding mode is analogous to the rounding policy used for float and double arithmetic in Java.
Rounding mode to assert that the requested operation has an exact result, hence no rounding is necessary. If this rounding mode is specified on an operation that yields an inexact result, an ArithmeticException is thrown.
Properties
Functions
Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)
Returns an array containing the constants of this enum type, in the order they're declared.