/*
* @(#)MathContext.java 1.5 06/04/07
*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
/*
* @(#)MathContext.java 1.x 01/xx/xx
*
* Copyright IBM Corporation, 1997, 2001. All Rights Reserved.
*
* This software is the proprietary information of Sun Microsystems, Inc.
* and IBM Corporation. Use is subject to license terms.
*
*/
package java.math;
import java.io.*;
/**
* Immutable objects which encapsulate the context settings which
* describe certain rules for numerical operators, such as those
* implemented by the {@link BigDecimal} class.
*
* <p>The base-independent settings are:
* <ol>
* <li>{@code precision}:
* the number of digits to be used for an operation; results are
* rounded to this precision
*
* <li>{@code roundingMode}:
* a {@link RoundingMode} object which specifies the algorithm to be
* used for rounding.
* </ol>
*
* @see BigDecimal
* @see RoundingMode
* @author Mike Cowlishaw
* @author Joseph D. Darcy
* @since 1.5
*/
public final class MathContext implements Serializable {
/* ----- Constants ----- */
// defaults for constructors
private static final int DEFAULT_DIGITS = 9;
private static final RoundingMode DEFAULT_ROUNDINGMODE = RoundingMode.HALF_UP;
// Smallest values for digits (Maximum is Integer.MAX_VALUE)
private static final int MIN_DIGITS = 0;
// Serialization version
private static final long serialVersionUID = 5579720004786848255L;
/* ----- Public Properties ----- */
/**
* A {@code MathContext} object whose settings have the values
* required for unlimited precision arithmetic.
* The values of the settings are:
* <code>
* precision=0 roundingMode=HALF_UP
* </code>
*/
public static final MathContext UNLIMITED =
new MathContext(0, RoundingMode.HALF_UP);
/**
* A {@code MathContext} object with a precision setting
* matching the IEEE 754R Decimal32 format, 7 digits, and a
* rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}, the
* IEEE 754R default.
*/
public static final MathContext DECIMAL32 =
new MathContext(7, RoundingMode.HALF_EVEN);
/**
* A {@code MathContext} object with a precision setting
* matching the IEEE 754R Decimal64 format, 16 digits, and a
* rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}, the
* IEEE 754R default.
*/
public static final MathContext DECIMAL64 =
new MathContext(16, RoundingMode.HALF_EVEN);
/**
* A {@code MathContext} object with a precision setting
* matching the IEEE 754R Decimal128 format, 34 digits, and a
* rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}, the
* IEEE 754R default.
*/
public static final MathContext DECIMAL128 =
new MathContext(34, RoundingMode.HALF_EVEN);
/* ----- Shared Properties ----- */
/**
* The number of digits to be used for an operation. A value of 0
* indicates that unlimited precision (as many digits as are
* required) will be used. Note that leading zeros (in the
* coefficient of a number) are never significant.
*
* <p>{@code precision} will always be non-negative.
*
* @serial
*/
final int precision;
/**
* The rounding algorithm to be used for an operation.
*
* @see RoundingMode
* @serial
*/
final RoundingMode roundingMode;
/**
* Lookaside for the rounding points (the numbers which determine
* whether the coefficient of a number will require rounding).
* These will be present if {@code precision > 0} and
* {@code precision <= MAX_LOOKASIDE}. In this case they will share the
* {@code BigInteger int[]} array. Note that the transients
* cannot be {@code final} because they are reconstructed on
* deserialization.
*/
transient BigInteger roundingMax = null;
transient BigInteger roundingMin = null;
private static final int MAX_LOOKASIDE = 1000;
/* ----- Constructors ----- */
/**
* Constructs a new {@code MathContext} with the specified
* precision and the {@link RoundingMode#HALF_UP HALF_UP} rounding
* mode.
*
* @param setPrecision The non-negative {@code int} precision setting.
* @throws IllegalArgumentException if the {@code setPrecision} parameter is less
* than zero.
*/
public MathContext(int setPrecision) {
this(setPrecision, DEFAULT_ROUNDINGMODE);
return;
}
/**
* Constructs a new {@code MathContext} with a specified
* precision and rounding mode.
*
* @param setPrecision The non-negative {@code int} precision setting.
* @param setRoundingMode The rounding mode to use.
* @throws IllegalArgumentException if the {@code setPrecision} parameter is less
* than zero.
* @throws NullPointerException if the rounding mode argument is {@code null}
*/
public MathContext(int setPrecision,
RoundingMode setRoundingMode) {
if (setPrecision < MIN_DIGITS)
throw new IllegalArgumentException("Digits < 0");
if (setRoundingMode == null)
throw new NullPointerException("null RoundingMode");
precision = setPrecision;
if (precision > 0 && precision <= MAX_LOOKASIDE) {
roundingMax = BigInteger.TEN.pow(precision);
roundingMin = roundingMax.negate();
}
roundingMode = setRoundingMode;
return;
}
/**
* Constructs a new {@code MathContext} from a string.
*
* The string must be in the same format as that produced by the
* {@link #toString} method.
*
* <p>An {@code IllegalArgumentException} is thrown if the precision
* section of the string is out of range ({@code < 0}) or the string is
* not in the format created by the {@link #toString} method.
*
* @param val The string to be parsed
* @throws IllegalArgumentException if the precision section is out of range
* or of incorrect format
* @throws NullPointerException if the argument is {@code null}
*/
public MathContext(String val) {
boolean bad = false;
int setPrecision;
if (val == null)
throw new NullPointerException("null String");
try { // any error here is a string format problem
if (!val.startsWith("precision=")) throw new RuntimeException();
int fence = val.indexOf(' '); // could be -1
int off = 10; // where value starts
setPrecision = Integer.parseInt(val.substring(10, fence));
if (!val.startsWith("roundingMode=", fence+1))
throw new RuntimeException();
off = fence + 1 + 13;
String str = val.substring(off, val.length());
roundingMode = RoundingMode.valueOf(str);
} catch (RuntimeException re) {
throw new IllegalArgumentException("bad string format");
}
if (setPrecision < MIN_DIGITS)
throw new IllegalArgumentException("Digits < 0");
// the other parameters cannot be invalid if we got here
precision = setPrecision;
if (precision > 0 && precision <= MAX_LOOKASIDE) {
roundingMax = BigInteger.TEN.pow(precision);
roundingMin = roundingMax.negate();
}
}
/**
* Returns the {@code precision} setting.
* This value is always non-negative.
*
* @return an {@code int} which is the value of the {@code precision}
* setting
*/
public int getPrecision() {
return precision;
}
/**
* Returns the roundingMode setting.
* This will be one of
* {@link RoundingMode#CEILING},
* {@link RoundingMode#DOWN},
* {@link RoundingMode#FLOOR},
* {@link RoundingMode#HALF_DOWN},
* {@link RoundingMode#HALF_EVEN},
* {@link RoundingMode#HALF_UP},
* {@link RoundingMode#UNNECESSARY}, or
* {@link RoundingMode#UP}.
*
* @return a {@code RoundingMode} object which is the value of the
* {@code roundingMode} setting
*/
public RoundingMode getRoundingMode() {
return roundingMode;
}
/**
* Compares this {@code MathContext} with the specified
* {@code Object} for equality.
*
* @param x {@code Object} to which this {@code MathContext} is to
* be compared.
* @return {@code true} if and only if the specified {@code Object} is
* a {@code MathContext} object which has exactly the same
* settings as this object
*/
public boolean equals(Object x){
MathContext mc;
if (!(x instanceof MathContext))
return false;
mc = (MathContext) x;
return mc.precision == this.precision
&& mc.roundingMode == this.roundingMode; // no need for .equals()
}
/**
* Returns the hash code for this {@code MathContext}.
*
* @return hash code for this {@code MathContext}
*/
public int hashCode() {
return this.precision + roundingMode.hashCode() * 59;
}
/**
* Returns the string representation of this {@code MathContext}.
* The {@code String} returned represents the settings of the
* {@code MathContext} object as two space-delimited words
* (separated by a single space character, <tt>'\u0020'</tt>,
* and with no leading or trailing white space), as follows:
* <ol>
* <li>
* The string {@code "precision="}, immediately followed
* by the value of the precision setting as a numeric string as if
* generated by the {@link Integer#toString(int) Integer.toString}
* method.
*
* <li>
* The string {@code "roundingMode="}, immediately
* followed by the value of the {@code roundingMode} setting as a
* word. This word will be the same as the name of the
* corresponding public constant in the {@link RoundingMode}
* enum.
* </ol>
* <p>
* For example:
* <pre>
* precision=9 roundingMode=HALF_UP
* </pre>
*
* Additional words may be appended to the result of
* {@code toString} in the future if more properties are added to
* this class.
*
* @return a {@code String} representing the context settings
*/
public java.lang.String toString() {
return "precision=" + precision + " " +
"roundingMode=" + roundingMode.toString();
}
// Private methods
/**
* Reconstitute the {@code MathContext} instance from a stream (that is,
* deserialize it).
*
* @param s the stream being read.
*/
private synchronized void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject(); // read in all fields
// validate possibly bad fields
if (precision < MIN_DIGITS) {
String message = "MathContext: invalid digits in stream";
throw new java.io.StreamCorruptedException(message);
}
if (roundingMode == null) {
String message = "MathContext: null roundingMode in stream";
throw new java.io.StreamCorruptedException(message);
}
// Set the lookaside, if applicable
if (precision <= MAX_LOOKASIDE) {
roundingMax = BigInteger.TEN.pow(precision);
roundingMin = roundingMax.negate();
}
}
}
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