/*
* @(#)RoundingMode.java 1.3 04/06/18
*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
/*
* @(#)RoundingMode.java 1.x 01/xx/xx
*
* Copyright 2001 Sun Microsystems, Inc. All Rights Reserved.
* Portions Copyright IBM Corporation, 2001. All Rights Reserved.
*
* This software is the proprietary information of Sun Microsystems, Inc.
* Use is subject to license terms.
*
*/
package java.math;
/**
* 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
* {@link MathContext} object with the proper settings
* (precision set to 1, and the
* roundingMode set to the rounding mode in question), and
* calling {@link BigDecimal#round 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 {@link BigDecimal}
* ({@link BigDecimal#ROUND_UP}, {@link BigDecimal#ROUND_DOWN},
* etc. ).
*
* @see BigDecimal
* @see MathContext
* @version 1.x 01/xx/xx
* @author Josh Bloch
* @author Mike Cowlishaw
* @author Joseph D. Darcy
*/
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:
*
*| 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 |
*
*/
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.
*
*Example:
*
*| 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 |
*
*/
DOWN(BigDecimal.ROUND_DOWN),
/**
* 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:
*
*| 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 |
*
*/
CEILING(BigDecimal.ROUND_CEILING),
/**
* 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:
*
*| 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 |
*
*/
FLOOR(BigDecimal.ROUND_FLOOR),
/**
* 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:
*
*| 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_UP(BigDecimal.ROUND_HALF_UP),
/**
* 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:
*
*| 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_DOWN(BigDecimal.ROUND_HALF_DOWN),
/**
* 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:
*
*| 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 |
*
*/
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
* ArithmeticException is thrown.
*Example:
*
*| 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 |
*
*/
UNNECESSARY(BigDecimal.ROUND_UNNECESSARY);
// Corresponding BigDecimal rounding constant
final int oldMode;
/**
* Constructor
*
* @param oldMode The BigDecimal constant corresponding to
* this mode
*/
private RoundingMode(int oldMode) {
this.oldMode = oldMode;
}
/**
* Returns the RoundingMode object corresponding to a
* legacy integer rounding mode constant in {@link BigDecimal}.
*
* @param rm legacy integer rounding mode to convert
* @return RoundingMode corresponding to the given integer.
* @throws IllegalArgumentException integer is out of range
*/
public static RoundingMode valueOf(int rm) {
switch(rm) {
case BigDecimal.ROUND_UP:
return UP;
case BigDecimal.ROUND_DOWN:
return DOWN;
case BigDecimal.ROUND_CEILING:
return CEILING;
case BigDecimal.ROUND_FLOOR:
return FLOOR;
case BigDecimal.ROUND_HALF_UP:
return HALF_UP;
case BigDecimal.ROUND_HALF_DOWN:
return HALF_DOWN;
case BigDecimal.ROUND_HALF_EVEN:
return HALF_EVEN;
case BigDecimal.ROUND_UNNECESSARY:
return UNNECESSARY;
default:
throw new IllegalArgumentException("argument out of range");
}
}
}