Serializable
, Comparable<RoundingMode>
, Constable
public enum RoundingMode extends Enum<RoundingMode>
More generally, a rounding policy defines a mapping from the real numbers to a subset of representable values. In the case of BigDecimal
, the representable values are a function of the precision being used in the computation. Assuming the mathematical result is within the exponent range of BigDecimal
, the mathematical result will be exactly representable in the result precision or will fall between two adjacent representable values. In the case of falling between two representable values, the rounding policy determines which of those two bracketing values is the result. For in-range real numbers, for a given set of representable values, a rounding policy maps a continuous segment of the real number line to a single representable value where the real number numerically equal to a representable value is mapped to that value.
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. ).
Enum.EnumDesc<E extends Enum<E>>
Enum Constant | Description |
---|---|
CEILING |
Rounding mode to round towards positive infinity. |
DOWN |
Rounding mode to round towards zero. |
FLOOR |
Rounding mode to round towards negative infinity. |
HALF_DOWN |
Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round down. |
HALF_EVEN |
Rounding mode to round towards the "nearest neighbor" unless both neighbors are equidistant, in which case, round towards the even neighbor. |
HALF_UP |
Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round up. |
UNNECESSARY |
Rounding mode to assert that the requested operation has an exact result, hence no rounding is necessary. |
UP |
Rounding mode to round away from zero. |
Modifier and Type | Method | Description |
---|---|---|
static RoundingMode |
valueOf |
Returns the RoundingMode object corresponding to a legacy integer rounding mode constant in BigDecimal . |
static RoundingMode |
valueOf |
Returns the enum constant of this class with the specified name. |
static RoundingMode[] |
values() |
Returns an array containing the constants of this enum class, in the order they are declared. |
public static final RoundingMode UP
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 static final RoundingMode DOWN
float
and double
operators remainder and conversion to an integer value (JLS 15.4). This mode corresponds to the IEEE 754 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 |
public static final RoundingMode CEILING
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 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 |
public static final RoundingMode FLOOR
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 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 |
public static final RoundingMode HALF_UP
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 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 |
public static final RoundingMode HALF_DOWN
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 |
public static final RoundingMode HALF_EVEN
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.float
and double
arithmetic operators in Java (JLS 15.4). This mode corresponds to the IEEE 754 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 |
public static final RoundingMode UNNECESSARY
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
|
public static RoundingMode[] values()
public static RoundingMode valueOf(String name)
name
- the name of the enum constant to be returned.IllegalArgumentException
- if this enum class has no constant with the specified nameNullPointerException
- if the argument is nullpublic static RoundingMode valueOf(int rm)
RoundingMode
object corresponding to a legacy integer rounding mode constant in BigDecimal
.rm
- legacy integer rounding mode to convertRoundingMode
corresponding to the given integer.IllegalArgumentException
- integer is out of range
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/math/RoundingMode.html