java.math.RoundingMode

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

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 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.

**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`

This enum is intended to replace the integer-based 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 rounding direction attributes defined in the IEEE Standard for Floating-Point Arithmetic, IEEE 754-2019. Where present, this correspondence will be noted in the documentation of the particular constant.
Since:: 1.5
See Also:: BigDecimal, MathContext

Nested Class Summary

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

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 class with the specified name.

static RoundingMode[]

values()

Returns an array containing the constants of this enum class, in the 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
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 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. This mode corresponds to the IEEE 754-2019 rounding attribute roundTowardZero.
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 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. This mode corresponds to the IEEE 754-2019 rounding attribute roundTowardPositive.
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 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. This mode corresponds to the IEEE 754-2019 rounding attribute roundTowardNegative.
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 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. This mode corresponds to the IEEE 754-2019 rounding attribute roundTiesToAway.
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 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 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. This mode corresponds to the IEEE 754-2019 rounding attribute roundTiesToEven.
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 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 Details
- values
  
  public static RoundingMode[] 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
  
  public static RoundingMode valueOf(String name)
  
  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 name
  
  NullPointerException - if the argument is null
- valueOf
  
  public static RoundingMode valueOf(int rm)
  
  Returns the RoundingMode object corresponding to a legacy integer rounding mode constant in BigDecimal.
  
  Parameters:
  
  rm - legacy integer rounding mode to convert
  
  Returns:
  
  RoundingMode corresponding to the given integer.
  
  Throws:
  
  IllegalArgumentException - integer is out of range

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