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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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*
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*
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/*
* Portions Copyright IBM Corporation, 2001. All Rights Reserved.
*/
package java.math;
/**
* Specifies a rounding 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 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
* {@code BigDecimal} number with the specified value, forming a
* {@link MathContext} object with the proper settings
* ({@code precision} set to {@code 1}, and the
* {@code roundingMode} set to the rounding mode in question), and
* calling {@link BigDecimal#round round} on this number with the
* proper {@code 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 |
*
|---|
* | {@code UP} |
* {@code DOWN} |
* {@code CEILING} |
* {@code FLOOR} |
* {@code HALF_UP} |
* {@code HALF_DOWN} |
* {@code HALF_EVEN} |
* {@code UNNECESSARY} |
*
*
*
* | 5.5 | 6 | 5 | 6 | 5 | 6 | 5 | 6 | throw {@code ArithmeticException} |
*
|---|
| 2.5 | 3 | 2 | 3 | 2 | 3 | 2 | 2 | throw {@code ArithmeticException} |
*
|---|
| 1.6 | 2 | 1 | 2 | 1 | 2 | 2 | 2 | throw {@code ArithmeticException} |
*
|---|
| 1.1 | 2 | 1 | 2 | 1 | 1 | 1 | 1 | throw {@code 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 {@code ArithmeticException} |
*
|---|
| -1.6 | -2 | -1 | -1 | -2 | -2 | -2 | -2 | throw {@code ArithmeticException} |
*
|---|
| -2.5 | -3 | -2 | -2 | -3 | -3 | -2 | -2 | throw {@code ArithmeticException} |
*
|---|
| -5.5 | -6 | -5 | -5 | -6 | -6 | -5 | -6 | throw {@code ArithmeticException} |
*
|---|
*
*
*
* This {@code enum} is intended to replace the integer-based
* enumeration of rounding mode constants in {@link BigDecimal}
* ({@link BigDecimal#ROUND_UP}, {@link BigDecimal#ROUND_DOWN},
* etc. ).
*
* @apiNote
* 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.
*
* @see BigDecimal
* @see MathContext
* @author Josh Bloch
* @author Mike Cowlishaw
* @author Joseph D. Darcy
* @since 1.5
*/
@SuppressWarnings("deprecation") // Legacy rounding mode constants in BigDecimal
public enum RoundingMode {
/**
* 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 {@code 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 |
*
|---|
*
*/
UP(BigDecimal.ROUND_UP),
/**
* 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-direction
* attribute roundTowardZero.
*
*Example:
*
* Rounding mode DOWN Examples
*
*| Input Number |
* Input rounded to one digit
with {@code 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 |
*
|---|
*
*/
DOWN(BigDecimal.ROUND_DOWN),
/**
* Rounding mode to round towards positive infinity. If the
* result is positive, behaves as for {@code RoundingMode.UP};
* if negative, behaves as for {@code RoundingMode.DOWN}. Note
* that this rounding mode never decreases the calculated value.
* This mode corresponds to the IEEE 754-2019 rounding-direction
* attribute roundTowardPositive.
*
*Example:
*
* Rounding mode CEILING Examples
*
*| Input Number |
* Input rounded to one digit
with {@code 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 |
*
|---|
*
*/
CEILING(BigDecimal.ROUND_CEILING),
/**
* Rounding mode to round towards negative infinity. If the
* result is positive, behave as for {@code RoundingMode.DOWN};
* if negative, behave as for {@code RoundingMode.UP}. Note that
* this rounding mode never increases the calculated value.
* This mode corresponds to the IEEE 754-2019 rounding-direction
* attribute roundTowardNegative.
*
*Example:
*
* Rounding mode FLOOR Examples
*
*| Input Number |
* Input rounded to one digit
with {@code 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 |
*
|---|
*
*/
FLOOR(BigDecimal.ROUND_FLOOR),
/**
* Rounding mode to round towards {@literal "nearest neighbor"}
* unless both neighbors are equidistant, in which case round up.
* Behaves as for {@code RoundingMode.UP} if the discarded
* fraction is ≥ 0.5; otherwise, behaves as for
* {@code RoundingMode.DOWN}. Note that this is the rounding
* mode commonly taught at school.
* This mode corresponds to the IEEE 754-2019 rounding-direction
* attribute roundTiesToAway.
*
*Example:
*
* Rounding mode HALF_UP Examples
*
*| Input Number |
* Input rounded to one digit
with {@code 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_UP(BigDecimal.ROUND_HALF_UP),
/**
* Rounding mode to round towards {@literal "nearest neighbor"}
* unless both neighbors are equidistant, in which case round
* down. Behaves as for {@code RoundingMode.UP} if the discarded
* fraction is > 0.5; otherwise, behaves as for
* {@code RoundingMode.DOWN}.
*
*Example:
*
* Rounding mode HALF_DOWN Examples
*
*| Input Number |
* Input rounded to one digit
with {@code 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_DOWN(BigDecimal.ROUND_HALF_DOWN),
/**
* Rounding mode to round towards the {@literal "nearest neighbor"}
* unless both neighbors are equidistant, in which case, round
* towards the even neighbor. Behaves as for
* {@code RoundingMode.HALF_UP} if the digit to the left of the
* discarded fraction is odd; behaves as for
* {@code 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 {@literal "Banker's rounding,"} and is
* chiefly used in the USA. This rounding mode is analogous to
* the rounding policy used for {@code float} and {@code double}
* arithmetic in Java.
* This mode corresponds to the IEEE 754-2019 rounding-direction
* attribute roundTiesToEven.
*
*Example:
*
* Rounding mode HALF_EVEN Examples
*
*| Input Number |
* Input rounded to one digit
with {@code 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 |
*
|---|
*
*/
HALF_EVEN(BigDecimal.ROUND_HALF_EVEN),
/**
* 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
* {@code ArithmeticException} is thrown.
*Example:
*
* Rounding mode UNNECESSARY Examples
*
*| Input Number |
* Input rounded to one digit
with {@code UNNECESSARY} rounding
* |
|---|
*
*| 5.5 | throw {@code ArithmeticException} |
*
|---|
| 2.5 | throw {@code ArithmeticException} |
*
|---|
| 1.6 | throw {@code ArithmeticException} |
*
|---|
| 1.1 | throw {@code ArithmeticException} |
*
|---|
| 1.0 | 1 |
*
|---|
| -1.0 | -1 |
*
|---|
| -1.1 | throw {@code ArithmeticException} |
*
|---|
| -1.6 | throw {@code ArithmeticException} |
*
|---|
| -2.5 | throw {@code ArithmeticException} |
*
|---|
| -5.5 | throw {@code ArithmeticException} |
*
|---|
*
*/
UNNECESSARY(BigDecimal.ROUND_UNNECESSARY);
// Corresponding BigDecimal rounding constant
final int oldMode;
/**
* Constructor
*
* @param oldMode The {@code BigDecimal} constant corresponding to
* this mode
*/
private RoundingMode(int oldMode) {
this.oldMode = oldMode;
}
/**
* Returns the {@code RoundingMode} object corresponding to a
* legacy integer rounding mode constant in {@link BigDecimal}.
*
* @param rm legacy integer rounding mode to convert
* @return {@code RoundingMode} corresponding to the given integer.
* @throws IllegalArgumentException integer is out of range
*/
public static RoundingMode valueOf(int rm) {
return switch (rm) {
case BigDecimal.ROUND_UP -> UP;
case BigDecimal.ROUND_DOWN -> DOWN;
case BigDecimal.ROUND_CEILING -> CEILING;
case BigDecimal.ROUND_FLOOR -> FLOOR;
case BigDecimal.ROUND_HALF_UP -> HALF_UP;
case BigDecimal.ROUND_HALF_DOWN -> HALF_DOWN;
case BigDecimal.ROUND_HALF_EVEN -> HALF_EVEN;
case BigDecimal.ROUND_UNNECESSARY -> UNNECESSARY;
default -> throw new IllegalArgumentException("argument out of range");
};
}
}