RoundingMode
public
final
enum
RoundingMode
extends Enum<RoundingMode>
java.lang.Object | ||
↳ | java.lang.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. ).
See also:
Summary
Enum values | |
---|---|
RoundingMode |
CEILING
Rounding mode to round towards positive infinity. |
RoundingMode |
DOWN
Rounding mode to round towards zero. |
RoundingMode |
FLOOR
Rounding mode to round towards negative infinity. |
RoundingMode |
HALF_DOWN
Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round down. |
RoundingMode |
HALF_EVEN
Rounding mode to round towards the "nearest neighbor" unless both neighbors are equidistant, in which case, round towards the even neighbor. |
RoundingMode |
HALF_UP
Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round up. |
RoundingMode |
UNNECESSARY
Rounding mode to assert that the requested operation has an exact result, hence no rounding is necessary. |
RoundingMode |
UP
Rounding mode to round away from zero. |
Public methods | |
---|---|
static
RoundingMode
|
valueOf(String name)
|
static
RoundingMode
|
valueOf(int rm)
Returns the |
static
final
RoundingMode[]
|
values()
|
Inherited methods | |
---|---|
Enum values
CEILING
public static final RoundingMode CEILING
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
public static final RoundingMode DOWN
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
public static final RoundingMode FLOOR
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
public static final RoundingMode HALF_DOWN
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
public static final RoundingMode 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
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
public static final RoundingMode HALF_UP
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
public static final RoundingMode UNNECESSARY
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
public static final RoundingMode UP
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
public static RoundingMode valueOf (String name)
Parameters | |
---|---|
name |
String |
Returns | |
---|---|
RoundingMode |
valueOf
public static RoundingMode valueOf (int rm)
Returns the RoundingMode
object corresponding to a
legacy integer rounding mode constant in BigDecimal
.
Parameters | |
---|---|
rm |
int : legacy integer rounding mode to convert |
Returns | |
---|---|
RoundingMode |
RoundingMode corresponding to the given integer. |
Throws | |
---|---|
IllegalArgumentException |
integer is out of range |
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Last updated 2024-04-11 UTC.