/*
* @(#)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 <i>rounding behavior</i> 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 <i>discarded fraction</i> 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.
*
* <p>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
* <tt>BigDecimal</tt> number with the specified value, forming a
* {@link MathContext} object with the proper settings
* (<tt>precision</tt> set to <tt>1</tt>, and the
* <tt>roundingMode</tt> set to the rounding mode in question), and
* calling {@link BigDecimal#round round} on this number with the
* proper <tt>MathContext</tt>. A summary table showing the results
* of these rounding operations for all rounding modes appears below.
*
*<p>
*<table border>
* <caption top><h3>Summary of Rounding Operations Under Different Rounding Modes</h3></caption>
* <tr><th></th><th colspan=8>Result of rounding input to one digit with the given
* rounding mode</th>
* <tr valign=top>
* <th>Input Number</th> <th><tt>UP</tt></th>
* <th><tt>DOWN</tt></th>
* <th><tt>CEILING</tt></th>
* <th><tt>FLOOR</tt></th>
* <th><tt>HALF_UP</tt></th>
* <th><tt>HALF_DOWN</tt></th>
* <th><tt>HALF_EVEN</tt></th>
* <th><tt>UNNECESSARY</tt></th>
*
* <tr align=right><td>5.5</td> <td>6</td> <td>5</td> <td>6</td> <td>5</td> <td>6</td> <td>5</td> <td>6</td> <td>throw <tt>ArithmeticException</tt></td>
* <tr align=right><td>2.5</td> <td>3</td> <td>2</td> <td>3</td> <td>2</td> <td>3</td> <td>2</td> <td>2</td> <td>throw <tt>ArithmeticException</tt></td>
* <tr align=right><td>1.6</td> <td>2</td> <td>1</td> <td>2</td> <td>1</td> <td>2</td> <td>2</td> <td>2</td> <td>throw <tt>ArithmeticException</tt></td>
* <tr align=right><td>1.1</td> <td>2</td> <td>1</td> <td>2</td> <td>1</td> <td>1</td> <td>1</td> <td>1</td> <td>throw <tt>ArithmeticException</tt></td>
* <tr align=right><td>1.0</td> <td>1</td> <td>1</td> <td>1</td> <td>1</td> <td>1</td> <td>1</td> <td>1</td> <td>1</td>
* <tr align=right><td>-1.0</td> <td>-1</td> <td>-1</td> <td>-1</td> <td>-1</td> <td>-1</td> <td>-1</td> <td>-1</td> <td>-1</td>
* <tr align=right><td>-1.1</td> <td>-2</td> <td>-1</td> <td>-1</td> <td>-2</td> <td>-1</td> <td>-1</td> <td>-1</td> <td>throw <tt>ArithmeticException</tt></td>
* <tr align=right><td>-1.6</td> <td>-2</td> <td>-1</td> <td>-1</td> <td>-2</td> <td>-2</td> <td>-2</td> <td>-2</td> <td>throw <tt>ArithmeticException</tt></td>
* <tr align=right><td>-2.5</td> <td>-3</td> <td>-2</td> <td>-2</td> <td>-3</td> <td>-3</td> <td>-2</td> <td>-2</td> <td>throw <tt>ArithmeticException</tt></td>
* <tr align=right><td>-5.5</td> <td>-6</td> <td>-5</td> <td>-5</td> <td>-6</td> <td>-6</td> <td>-5</td> <td>-6</td> <td>throw <tt>ArithmeticException</tt></td>
*</table>
*
*
* <p>This <tt>enum</tt> 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.
*
*<p>Example:
*<table border>
*<tr valign=top><th>Input Number</th>
* <th>Input rounded to one digit<br> with <tt>UP</tt> rounding
*<tr align=right><td>5.5</td> <td>6</td>
*<tr align=right><td>2.5</td> <td>3</td>
*<tr align=right><td>1.6</td> <td>2</td>
*<tr align=right><td>1.1</td> <td>2</td>
*<tr align=right><td>1.0</td> <td>1</td>
*<tr align=right><td>-1.0</td> <td>-1</td>
*<tr align=right><td>-1.1</td> <td>-2</td>
*<tr align=right><td>-1.6</td> <td>-2</td>
*<tr align=right><td>-2.5</td> <td>-3</td>
*<tr align=right><td>-5.5</td> <td>-6</td>
*</table>
*/
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.
*
*<p>Example:
*<table border>
*<tr valign=top><th>Input Number</th>
* <th>Input rounded to one digit<br> with <tt>DOWN</tt> rounding
*<tr align=right><td>5.5</td> <td>5</td>
*<tr align=right><td>2.5</td> <td>2</td>
*<tr align=right><td>1.6</td> <td>1</td>
*<tr align=right><td>1.1</td> <td>1</td>
*<tr align=right><td>1.0</td> <td>1</td>
*<tr align=right><td>-1.0</td> <td>-1</td>
*<tr align=right><td>-1.1</td> <td>-1</td>
*<tr align=right><td>-1.6</td> <td>-1</td>
*<tr align=right><td>-2.5</td> <td>-2</td>
*<tr align=right><td>-5.5</td> <td>-5</td>
*</table>
*/
DOWN(BigDecimal.ROUND_DOWN),
/**
* Rounding mode to round towards positive infinity. If the
* result is positive, behaves as for <tt>RoundingMode.UP</tt>;
* if negative, behaves as for <tt>RoundingMode.DOWN</tt>. Note
* that this rounding mode never decreases the calculated value.
*
*<p>Example:
*<table border>
*<tr valign=top><th>Input Number</th>
* <th>Input rounded to one digit<br> with <tt>CEILING</tt> rounding
*<tr align=right><td>5.5</td> <td>6</td>
*<tr align=right><td>2.5</td> <td>3</td>
*<tr align=right><td>1.6</td> <td>2</td>
*<tr align=right><td>1.1</td> <td>2</td>
*<tr align=right><td>1.0</td> <td>1</td>
*<tr align=right><td>-1.0</td> <td>-1</td>
*<tr align=right><td>-1.1</td> <td>-1</td>
*<tr align=right><td>-1.6</td> <td>-1</td>
*<tr align=right><td>-2.5</td> <td>-2</td>
*<tr align=right><td>-5.5</td> <td>-5</td>
*</table>
*/
CEILING(BigDecimal.ROUND_CEILING),
/**
* Rounding mode to round towards negative infinity. If the
* result is positive, behave as for <tt>RoundingMode.DOWN</tt>;
* if negative, behave as for <tt>RoundingMode.UP</tt>. Note that
* this rounding mode never increases the calculated value.
*
*<p>Example:
*<table border>
*<tr valign=top><th>Input Number</th>
* <th>Input rounded to one digit<br> with <tt>FLOOR</tt> rounding
*<tr align=right><td>5.5</td> <td>5</td>
*<tr align=right><td>2.5</td> <td>2</td>
*<tr align=right><td>1.6</td> <td>1</td>
*<tr align=right><td>1.1</td> <td>1</td>
*<tr align=right><td>1.0</td> <td>1</td>
*<tr align=right><td>-1.0</td> <td>-1</td>
*<tr align=right><td>-1.1</td> <td>-2</td>
*<tr align=right><td>-1.6</td> <td>-2</td>
*<tr align=right><td>-2.5</td> <td>-3</td>
*<tr align=right><td>-5.5</td> <td>-6</td>
*</table>
*/
FLOOR(BigDecimal.ROUND_FLOOR),
/**
* Rounding mode to round towards "nearest neighbor"
* unless both neighbors are equidistant, in which case round up.
* Behaves as for <tt>RoundingMode.UP</tt> if the discarded
* fraction is >= 0.5; otherwise, behaves as for
* <tt>RoundingMode.DOWN</tt>. Note that this is the rounding
* mode commonly taught at school.
*
*<p>Example:
*<table border>
*<tr valign=top><th>Input Number</th>
* <th>Input rounded to one digit<br> with <tt>HALF_UP</tt> rounding
*<tr align=right><td>5.5</td> <td>6</td>
*<tr align=right><td>2.5</td> <td>3</td>
*<tr align=right><td>1.6</td> <td>2</td>
*<tr align=right><td>1.1</td> <td>1</td>
*<tr align=right><td>1.0</td> <td>1</td>
*<tr align=right><td>-1.0</td> <td>-1</td>
*<tr align=right><td>-1.1</td> <td>-1</td>
*<tr align=right><td>-1.6</td> <td>-2</td>
*<tr align=right><td>-2.5</td> <td>-3</td>
*<tr align=right><td>-5.5</td> <td>-6</td>
*</table>
*/
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 <tt>RoundingMode.UP</tt> if the discarded
* fraction is > 0.5; otherwise, behaves as for
* <tt>RoundingMode.DOWN</tt>.
*
*<p>Example:
*<table border>
*<tr valign=top><th>Input Number</th>
* <th>Input rounded to one digit<br> with <tt>HALF_DOWN</tt> rounding
*<tr align=right><td>5.5</td> <td>5</td>
*<tr align=right><td>2.5</td> <td>2</td>
*<tr align=right><td>1.6</td> <td>2</td>
*<tr align=right><td>1.1</td> <td>1</td>
*<tr align=right><td>1.0</td> <td>1</td>
*<tr align=right><td>-1.0</td> <td>-1</td>
*<tr align=right><td>-1.1</td> <td>-1</td>
*<tr align=right><td>-1.6</td> <td>-2</td>
*<tr align=right><td>-2.5</td> <td>-2</td>
*<tr align=right><td>-5.5</td> <td>-5</td>
*</table>
*/
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
* <tt>RoundingMode.HALF_UP</tt> if the digit to the left of the
* discarded fraction is odd; behaves as for
* <tt>RoundingMode.HALF_DOWN</tt> 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 <tt>float</tt> and <tt>double</tt>
* arithmetic in Java.
*
*<p>Example:
*<table border>
*<tr valign=top><th>Input Number</th>
* <th>Input rounded to one digit<br> with <tt>HALF_EVEN</tt> rounding
*<tr align=right><td>5.5</td> <td>6</td>
*<tr align=right><td>2.5</td> <td>2</td>
*<tr align=right><td>1.6</td> <td>2</td>
*<tr align=right><td>1.1</td> <td>1</td>
*<tr align=right><td>1.0</td> <td>1</td>
*<tr align=right><td>-1.0</td> <td>-1</td>
*<tr align=right><td>-1.1</td> <td>-1</td>
*<tr align=right><td>-1.6</td> <td>-2</td>
*<tr align=right><td>-2.5</td> <td>-2</td>
*<tr align=right><td>-5.5</td> <td>-6</td>
*</table>
*/
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
* <tt>ArithmeticException</tt> is thrown.
*<p>Example:
*<table border>
*<tr valign=top><th>Input Number</th>
* <th>Input rounded to one digit<br> with <tt>UNNECESSARY</tt> rounding
*<tr align=right><td>5.5</td> <td>throw <tt>ArithmeticException</tt></td>
*<tr align=right><td>2.5</td> <td>throw <tt>ArithmeticException</tt></td>
*<tr align=right><td>1.6</td> <td>throw <tt>ArithmeticException</tt></td>
*<tr align=right><td>1.1</td> <td>throw <tt>ArithmeticException</tt></td>
*<tr align=right><td>1.0</td> <td>1</td>
*<tr align=right><td>-1.0</td> <td>-1</td>
*<tr align=right><td>-1.1</td> <td>throw <tt>ArithmeticException</tt></td>
*<tr align=right><td>-1.6</td> <td>throw <tt>ArithmeticException</tt></td>
*<tr align=right><td>-2.5</td> <td>throw <tt>ArithmeticException</tt></td>
*<tr align=right><td>-5.5</td> <td>throw <tt>ArithmeticException</tt></td>
*</table>
*/
UNNECESSARY(BigDecimal.ROUND_UNNECESSARY);
// Corresponding BigDecimal rounding constant
final int oldMode;
/**
* Constructor
*
* @param oldMode The <tt>BigDecimal</tt> constant corresponding to
* this mode
*/
private RoundingMode(int oldMode) {
this.oldMode = oldMode;
}
/**
* Returns the <tt>RoundingMode</tt> object corresponding to a
* legacy integer rounding mode constant in {@link BigDecimal}.
*
* @param rm legacy integer rounding mode to convert
* @return <tt>RoundingMode</tt> 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");
}
}
}
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