RoundingMode
class RoundingMode
kotlin.Any | ||
↳ | kotlin.Enum<java.math.RoundingMode> | |
↳ | java.math.RoundingMode |
Specifies a rounding policy 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. ).
Summary
Enum values | |
---|---|
Rounding mode to round towards positive infinity. |
|
Rounding mode to round towards zero. |
|
Rounding mode to round towards negative infinity. |
|
Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round down. |
|
Rounding mode to round towards the "nearest neighbor" unless both neighbors are equidistant, in which case, round towards the even neighbor. |
|
Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round up. |
|
Rounding mode to assert that the requested operation has an exact result, hence no rounding is necessary. |
|
Rounding mode to round away from zero. |
Public methods | |
---|---|
static RoundingMode! |
Returns the |
Enum values
CEILING
enum val CEILING : RoundingMode
Rounding mode to round towards positive infinity. If the result is positive, behaves as for RoundingMode.UP
; if negative, behaves as for RoundingMode.DOWN
. Note that this rounding mode never decreases the calculated value. This mode corresponds to the IEEE 754-2019 rounding-direction attribute roundTowardPositive.
Example:
Input Number | Input rounded to one digit with CEILING rounding |
---|---|
5.5 | 6 |
2.5 | 3 |
1.6 | 2 |
1.1 | 2 |
1.0 | 1 |
-1.0 | -1 |
-1.1 | -1 |
-1.6 | -1 |
-2.5 | -2 |
-5.5 | -5 |
DOWN
enum val DOWN : RoundingMode
Rounding mode to round towards zero. Never increments the digit prior to a discarded fraction (i.e., truncates). Note that this rounding mode never increases the magnitude of the calculated value. This mode corresponds to the IEEE 754-2019 rounding-direction attribute roundTowardZero.
Example:
Input Number | Input rounded to one digit with DOWN rounding |
---|---|
5.5 | 5 |
2.5 | 2 |
1.6 | 1 |
1.1 | 1 |
1.0 | 1 |
-1.0 | -1 |
-1.1 | -1 |
-1.6 | -1 |
-2.5 | -2 |
-5.5 | -5 |
FLOOR
enum val FLOOR : RoundingMode
Rounding mode to round towards negative infinity. If the result is positive, behave as for RoundingMode.DOWN
; if negative, behave as for RoundingMode.UP
. Note that this rounding mode never increases the calculated value. This mode corresponds to the IEEE 754-2019 rounding-direction attribute roundTowardNegative.
Example:
Input Number | Input rounded to one digit with FLOOR rounding |
---|---|
5.5 | 5 |
2.5 | 2 |
1.6 | 1 |
1.1 | 1 |
1.0 | 1 |
-1.0 | -1 |
-1.1 | -2 |
-1.6 | -2 |
-2.5 | -3 |
-5.5 | -6 |
HALF_DOWN
enum val HALF_DOWN : RoundingMode
Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round down. Behaves as for RoundingMode.UP
if the discarded fraction is > 0.5; otherwise, behaves as for RoundingMode.DOWN
.
Example:
Input Number | Input rounded to one digit with HALF_DOWN rounding |
---|---|
5.5 | 5 |
2.5 | 2 |
1.6 | 2 |
1.1 | 1 |
1.0 | 1 |
-1.0 | -1 |
-1.1 | -1 |
-1.6 | -2 |
-2.5 | -2 |
-5.5 | -5 |
HALF_EVEN
enum val HALF_EVEN : RoundingMode
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. This mode corresponds to the IEEE 754-2019 rounding-direction attribute roundTiesToEven.
Example:
Input Number | Input rounded to one digit with HALF_EVEN rounding |
---|---|
5.5 | 6 |
2.5 | 2 |
1.6 | 2 |
1.1 | 1 |
1.0 | 1 |
-1.0 | -1 |
-1.1 | -1 |
-1.6 | -2 |
-2.5 | -2 |
-5.5 | -6 |
HALF_UP
enum val HALF_UP : RoundingMode
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. This mode corresponds to the IEEE 754-2019 rounding-direction attribute roundTiesToAway.
Example:
Input Number | Input rounded to one digit with HALF_UP rounding |
---|---|
5.5 | 6 |
2.5 | 3 |
1.6 | 2 |
1.1 | 1 |
1.0 | 1 |
-1.0 | -1 |
-1.1 | -1 |
-1.6 | -2 |
-2.5 | -3 |
-5.5 | -6 |
UNNECESSARY
enum val UNNECESSARY : RoundingMode
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.
Example:
Input Number | Input rounded to one digit with UNNECESSARY rounding |
---|---|
5.5 | throw ArithmeticException |
2.5 | throw ArithmeticException |
1.6 | throw ArithmeticException |
1.1 | throw ArithmeticException |
1.0 | 1 |
-1.0 | -1 |
-1.1 | throw ArithmeticException |
-1.6 | throw ArithmeticException |
-2.5 | throw ArithmeticException |
-5.5 | throw ArithmeticException |
UP
enum val UP : RoundingMode
Rounding mode to round away from zero. Always increments the digit prior to a non-zero discarded fraction. Note that this rounding mode never decreases the magnitude of the calculated value.
Example:
Input Number | Input rounded to one digit with UP rounding |
---|---|
5.5 | 6 |
2.5 | 3 |
1.6 | 2 |
1.1 | 2 |
1.0 | 1 |
-1.0 | -1 |
-1.1 | -2 |
-1.6 | -2 |
-2.5 | -3 |
-5.5 | -6 |
Public methods
valueOf
static fun valueOf(rm: Int): RoundingMode!
Returns the RoundingMode
object corresponding to a legacy integer rounding mode constant in BigDecimal
.
Parameters | |
---|---|
rm |
Int: legacy integer rounding mode to convert |
Return | |
---|---|
RoundingMode! |
RoundingMode corresponding to the given integer. |
Exceptions | |
---|---|
java.lang.IllegalArgumentException |
integer is out of range |