Enum Class RoundingMode

java.lang.Object

java.lang.Enum<RoundingMode>

java.math.RoundingMode

All Implemented Interfaces:: Serializable,Comparable<RoundingMode>,Constable

public enumRoundingModeextendsEnum<RoundingMode>

Specifies arounding 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 thediscarded 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.

More generally, a rounding policy defines a mapping from the real numbers to a subset of representable values. In the case ofBigDecimal, the representable values are a function of theprecision being used in the computation. Assuming the mathematical result is within the exponent range ofBigDecimal, 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 aBigDecimal 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
Input Number	`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`

Thisenum is intended to replace the integer-based enumeration of rounding mode constants inBigDecimal (BigDecimal.ROUND_UP,BigDecimal.ROUND_DOWN, etc. ).

API Note:

Five of the rounding modes declared in this class correspond to rounding-direction attributes defined in theIEEE Standard for Floating-Point Arithmetic. Where present, this correspondence will be noted in the documentation of the particular constant.

SeeJava Language Specification:

15.4 Floating-point Expressions

Since:

1.5

External Specifications

IEEE Standard for Floating-Point Arithmetic

See Also:

Nested Class Summary
Nested classes/interfaces declared in class java.lang.Enum
Enum.EnumDesc<E extendsEnum<E>>
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
Modifier and Type
Method
Description
staticRoundingMode
valueOf(int rm)
Returns theRoundingMode object corresponding to a legacy integer rounding mode constant inBigDecimal.
staticRoundingMode
valueOf(String name)
Returns the enum constant of this class with the specified name.
staticRoundingMode[]
values()
Returns an array containing the constants of this enum class, inthe order they are declared.
Methods declared in class java.lang.Enum
clone,compareTo,describeConstable,equals,finalize,getDeclaringClass,hashCode,name,ordinal,toString,valueOf
Methods declared in class java.lang.Object
getClass,notify,notifyAll,wait,wait,wait

Enum Constant Details

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:
Rounding mode UP Examples
Input Number Input rounded to one digit
withUP 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
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.
API Note:
This rounding mode is analogous to the rounding policy used for thefloat anddouble operators remainder and conversion to an integer value (JLS15.4). This mode corresponds to the IEEE 754 rounding-direction attribute roundTowardZero.
Example:
Rounding mode DOWN Examples
Input Number Input rounded to one digit
withDOWN 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
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. This mode corresponds to the IEEE 754 rounding-direction attribute roundTowardPositive.
Example:
Rounding mode CEILING Examples
Input Number Input rounded to one digit
withCEILING 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
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. This mode corresponds to the IEEE 754 rounding-direction attribute roundTowardNegative.
Example:
Rounding mode FLOOR Examples
Input Number Input rounded to one digit
withFLOOR 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_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. This mode corresponds to the IEEE 754 rounding-direction attribute roundTiesToAway.
Example:
Rounding mode HALF_UP Examples
Input Number Input rounded to one digit
withHALF_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
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 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 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 mostfloat anddouble arithmetic operators in Java (JLS15.4). This mode corresponds to the IEEE 754 rounding-direction attribute roundTiesToEven.
Example:
Rounding mode HALF_EVEN Examples
Input Number Input rounded to one digit
withHALF_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

Rounding mode UP Examples
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

Rounding mode DOWN Examples
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

Rounding mode CEILING Examples
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

Rounding mode FLOOR Examples
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

Rounding mode HALF_UP Examples
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

Rounding mode HALF_DOWN Examples
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

Rounding mode HALF_EVEN Examples
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

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 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`

Method Details
- values
  public static RoundingMode[] values()
  Returns an array containing the constants of this enum class, inthe order they are declared.
  Returns:
  an array containing the constants of this enum class, in the order they are declared
- valueOf
  public static RoundingMode valueOf(String name)
  Returns the enum constant of this class with the specified name.The string must matchexactly an identifier used to declare anenum 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 name
  NullPointerException - 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

Movatterモバイル変換

Enum Class RoundingMode

Nested Class Summary

Nested classes/interfaces declared in class java.lang.Enum

Enum Constant Summary

Method Summary

Methods declared in class java.lang.Enum

Methods declared in class java.lang.Object

Enum Constant Details

UP

DOWN

CEILING

FLOOR

HALF_UP

HALF_DOWN

HALF_EVEN

UNNECESSARY

Method Details

values

valueOf

valueOf