RoundingMode (Java Platform SE 8 ) (original) (raw)
- 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 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 to 1, and theroundingMode 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.
Summary of Rounding Operations Under Different Rounding Modes
| 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 |
This enum is intended to replace the integer-based enumeration of rounding mode constants in BigDecimal (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 the RoundingMode object corresponding to a legacy integer rounding mode constant in BigDecimal. 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. * ### Methods inherited from class java.lang.[Enum](../../java/lang/Enum.html "class in java.lang") `[clone](../../java/lang/Enum.html#clone--), [compareTo](../../java/lang/Enum.html#compareTo-E-), [equals](../../java/lang/Enum.html#equals-java.lang.Object-), [finalize](../../java/lang/Enum.html#finalize--), [getDeclaringClass](../../java/lang/Enum.html#getDeclaringClass--), [hashCode](../../java/lang/Enum.html#hashCode--), [name](../../java/lang/Enum.html#name--), [ordinal](../../java/lang/Enum.html#ordinal--), [toString](../../java/lang/Enum.html#toString--), [valueOf](../../java/lang/Enum.html#valueOf-java.lang.Class-java.lang.String-)` * ### Methods inherited from class java.lang.[Object](../../java/lang/Object.html "class in java.lang") `[getClass](../../java/lang/Object.html#getClass--), [notify](../../java/lang/Object.html#notify--), [notifyAll](../../java/lang/Object.html#notifyAll--), [wait](../../java/lang/Object.html#wait--), [wait](../../java/lang/Object.html#wait-long-), [wait](../../java/lang/Object.html#wait-long-int-)`Enum Constant Detail
* #### UP public static final [RoundingMode](../../java/math/RoundingMode.html "enum in java.math") 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 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 | * #### DOWN public static final [RoundingMode](../../java/math/RoundingMode.html "enum in java.math") 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 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 | * #### CEILING public static final [RoundingMode](../../java/math/RoundingMode.html "enum in java.math") 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. Example: __**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 | * #### FLOOR public static final [RoundingMode](../../java/math/RoundingMode.html "enum in java.math") 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. Example: __**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 | * #### HALF\_UP public static final [RoundingMode](../../java/math/RoundingMode.html "enum in java.math") 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. Example: __**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 | * #### HALF\_DOWN public static final [RoundingMode](../../java/math/RoundingMode.html "enum in java.math") 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: __**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 | * #### HALF\_EVEN public static final [RoundingMode](../../java/math/RoundingMode.html "enum in java.math") 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. Example: __**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](../../java/math/RoundingMode.html "enum in java.math") 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: __**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 Detail
* #### values public static [RoundingMode](../../java/math/RoundingMode.html "enum in java.math")[] 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](../../java/math/RoundingMode.html "enum in java.math") valueOf([String](../../java/lang/String.html "class in java.lang") 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](../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if this enum type has no constant with the specified name `[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if the argument is null * #### valueOf public static [RoundingMode](../../java/math/RoundingMode.html "enum in java.math") valueOf(int rm) Returns the `RoundingMode` object corresponding to a legacy integer rounding mode constant in [BigDecimal](../../java/math/BigDecimal.html "class in java.math"). Parameters: `rm` \- legacy integer rounding mode to convert Returns: `RoundingMode` corresponding to the given integer. Throws: `[IllegalArgumentException](../../java/lang/IllegalArgumentException.html "class in java.lang")` \- integer is out of range
Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
Copyright © 1993, 2025, Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.