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/*
* Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* Portions Copyright IBM Corporation, 2001. All Rights Reserved.
*/
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
* {@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 BigAny#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
* Result of rounding input to one digit with the given
* rounding mode
*
* Input Number {@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 BigAny}
* ({@link BigAny#ROUND_UP}, {@link BigAny#ROUND_DOWN},
* etc. ).
*
* @see BigAny
* @see MathContext
* @author Josh Bloch
* @author Mike Cowlishaw
* @author Joseph D. Darcy
* @since 1.5
*/
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(BigAny.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:
*
* 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(BigAny.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.
*
*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(BigAny.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.
*
*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(BigAny.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.
*
*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(BigAny.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(BigAny.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.
*
*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(BigAny.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(BigAny.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 BigAny}.
*
* @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) {
switch(rm) {
case BigAny.ROUND_UP:
return UP;
case BigAny.ROUND_DOWN:
return DOWN;
case BigAny.ROUND_CEILING:
return CEILING;
case BigAny.ROUND_FLOOR:
return FLOOR;
case BigAny.ROUND_HALF_UP:
return HALF_UP;
case BigAny.ROUND_HALF_DOWN:
return HALF_DOWN;
case BigAny.ROUND_HALF_EVEN:
return HALF_EVEN;
case BigAny.ROUND_UNNECESSARY:
return UNNECESSARY;
default:
throw new IllegalArgumentException("argument out of range");
}
}
}