 java.lang.Object

 java.lang.Enum<RoundingMode>

 java.math.RoundingMode

 All Implemented Interfaces:
Serializable
,Comparable<RoundingMode>
public enum RoundingMode extends Enum<RoundingMode>
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 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 aMathContext
object with the proper settings (precision
set to1
, and theroundingMode
set to the rounding mode in question), and callinground
on this number with the properMathContext
. A summary table showing the results of these rounding operations for all rounding modes appears below.Summary of Rounding Operations Under Different Rounding Modes 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 inBigDecimal
(BigDecimal.ROUND_UP
,BigDecimal.ROUND_DOWN
, etc. ). Since:
 1.5
 See Also:
BigDecimal
,MathContext


Enum Constant Summary
Enum Constants 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.

Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static RoundingMode
valueOf(int rm)
Returns theRoundingMode
object corresponding to a legacy integer rounding mode constant inBigDecimal
.static RoundingMode
valueOf(String name)
Returns the enum constant of this type with the specified name.static RoundingMode[]
values()
Returns an array containing the constants of this enum type, in the order they are declared.



Enum Constant Detail

UP
public static final RoundingMode 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
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.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
public static final RoundingMode 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.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
public static final RoundingMode 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.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
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 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.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
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 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
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 forRoundingMode.HALF_UP
if the digit to the left of the discarded fraction is odd; behaves as forRoundingMode.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 forfloat
anddouble
arithmetic in Java.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
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, 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 Detail

values
public static RoundingMode[] values()
Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:for (RoundingMode c : RoundingMode.values()) System.out.println(c);
 Returns:
 an array containing the constants of this enum type, in the order they are declared

valueOf
public static RoundingMode valueOf(String name)
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.) Parameters:
name
 the name of the enum constant to be returned. Returns:
 the enum constant with the specified name
 Throws:
IllegalArgumentException
 if this enum type has no constant with the specified nameNullPointerException
 if the argument is null

valueOf
public static RoundingMode valueOf(int rm)
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

