 All Implemented Interfaces:
Serializable
,Comparable<RoundingMode>
,Constable
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 inrange
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 twodigit 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 integerbased
enumeration of rounding mode constants in BigDecimal
(BigDecimal.ROUND_UP
, BigDecimal.ROUND_DOWN
,
etc. ).
 API Note:
 Five of the rounding modes declared in this class correspond to roundingdirection attributes defined in the IEEE Standard for FloatingPoint Arithmetic. Where present, this correspondence will be noted in the documentation of the particular constant.
 See Java Language Specification:

15.4 Floatingpoint Expressions
 Since:
 1.5
 See Also:

Nested Class Summary
Nested classes/interfaces declared in class java.lang.Enum
Enum.EnumDesc<E extends Enum<E>>

Enum Constant Summary
Enum ConstantDescriptionRounding 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. 
Method Summary
Modifier and TypeMethodDescriptionstatic RoundingMode
valueOf
(int rm) Returns theRoundingMode
object corresponding to a legacy integer rounding mode constant inBigDecimal
.static RoundingMode
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.

Enum Constant Details

UP
Rounding mode to round away from zero. Always increments the digit prior to a nonzero discarded fraction. Note that this rounding mode never decreases the magnitude of the calculated value.Example:
Rounding mode UP Examples Input Number Input rounded to one digit
withUP
rounding5.5 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 
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. API Note:
 This rounding mode is analogous to the rounding policy used
for the
float
anddouble
operators remainder and conversion to an integer value (JLS 15.4). This mode corresponds to the IEEE 754 roundingdirection attribute roundTowardZero.Example:
Rounding mode DOWN Examples Input Number Input rounded to one digit
withDOWN
rounding5.5 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

CEILING
Rounding mode to round towards positive infinity. If the result is positive, behaves as forRoundingMode.UP
; if negative, behaves as forRoundingMode.DOWN
. Note that this rounding mode never decreases the calculated value. This mode corresponds to the IEEE 754 roundingdirection attribute roundTowardPositive.Example:
Rounding mode CEILING Examples Input Number Input rounded to one digit
withCEILING
rounding5.5 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 
FLOOR
Rounding mode to round towards negative infinity. If the result is positive, behave as forRoundingMode.DOWN
; if negative, behave as forRoundingMode.UP
. Note that this rounding mode never increases the calculated value. This mode corresponds to the IEEE 754 roundingdirection attribute roundTowardNegative.Example:
Rounding mode FLOOR Examples Input Number Input rounded to one digit
withFLOOR
rounding5.5 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_UP
Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round up. Behaves as forRoundingMode.UP
if the discarded fraction is ≥ 0.5; otherwise, behaves as forRoundingMode.DOWN
. Note that this is the rounding mode commonly taught at school. This mode corresponds to the IEEE 754 roundingdirection attribute roundTiesToAway.Example:
Rounding mode HALF_UP Examples Input Number Input rounded to one digit
withHALF_UP
rounding5.5 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 
HALF_DOWN
Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round down. Behaves as forRoundingMode.UP
if the discarded fraction is > 0.5; otherwise, behaves as forRoundingMode.DOWN
.Example:
Rounding mode HALF_DOWN Examples Input Number Input rounded to one digit
withHALF_DOWN
rounding5.5 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
Rounding mode to round towards the "nearest neighbor" unless both neighbors are equidistant, in which case, round towards the even neighbor. Behaves as forRoundingMode.HALF_UP
if the digit to the left of the discarded fraction is odd; behaves as forRoundingMode.HALF_DOWN
if it's even. API Note:
 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 most
float
anddouble
arithmetic operators in Java (JLS 15.4). This mode corresponds to the IEEE 754 roundingdirection attribute roundTiesToEven.Example:
Rounding mode HALF_EVEN Examples Input Number Input rounded to one digit
withHALF_EVEN
rounding5.5 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

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, anArithmeticException
is thrown.Example:
Rounding mode UNNECESSARY Examples Input Number Input rounded to one digit
withUNNECESSARY
rounding5.5 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


Method Details

values
Returns an array containing the constants of this enum class, in the order they are declared. Returns:
 an array containing the constants of this enum class, in the order they are declared

valueOf
Returns the enum constant of this class with the specified name. The string must match exactly an identifier used to declare an enum constant in this class. (Extraneous whitespace characters are not permitted.) Parameters:
name
 the name of the enum constant to be returned. Returns:
 the enum constant with the specified name
 Throws:
IllegalArgumentException
 if this enum class has no constant with the specified nameNullPointerException
 if the argument is null

valueOf
Returns theRoundingMode
object corresponding to a legacy integer rounding mode constant inBigDecimal
. Parameters:
rm
 legacy integer rounding mode to convert Returns:
RoundingMode
corresponding to the given integer. Throws:
IllegalArgumentException
 integer is out of range
