329 lines
12 KiB
Java
329 lines
12 KiB
Java
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/*
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* Copyright (c) 2003, 2021, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* Portions Copyright IBM Corporation, 1997, 2001. All Rights Reserved.
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*/
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package java.math;
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import java.io.*;
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/**
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* Immutable objects which encapsulate the context settings which
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* describe certain rules for numerical operators, such as those
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* implemented by the {@link BigDecimal} class.
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*
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* <p>The base-independent settings are:
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* <ol>
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* <li>{@code precision}:
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* the number of digits to be used for an operation; results are
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* rounded to this precision
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*
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* <li>{@code roundingMode}:
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* a {@link RoundingMode} object which specifies the algorithm to be
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* used for rounding.
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* </ol>
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*
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* @see BigDecimal
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* @see RoundingMode
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* @author Mike Cowlishaw
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* @author Joseph D. Darcy
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* @since 1.5
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*/
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public final class MathContext implements Serializable {
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/* ----- Constants ----- */
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// defaults for constructors
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private static final int DEFAULT_DIGITS = 9;
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private static final RoundingMode DEFAULT_ROUNDINGMODE = RoundingMode.HALF_UP;
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// Smallest values for digits (Maximum is Integer.MAX_VALUE)
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private static final int MIN_DIGITS = 0;
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// Serialization version
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@java.io.Serial
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private static final long serialVersionUID = 5579720004786848255L;
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/* ----- Public Properties ----- */
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/**
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* A {@code MathContext} object whose settings have the values
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* required for unlimited precision arithmetic.
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* The values of the settings are: {@code precision=0 roundingMode=HALF_UP}
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*/
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public static final MathContext UNLIMITED =
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new MathContext(0, RoundingMode.HALF_UP);
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/**
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* A {@code MathContext} object with a precision setting
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* matching the precision of the IEEE 754-2019 decimal32 format, 7 digits, and a
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* rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}.
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* Note the exponent range of decimal32 is <em>not</em> used for
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* rounding.
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*/
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public static final MathContext DECIMAL32 =
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new MathContext(7, RoundingMode.HALF_EVEN);
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/**
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* A {@code MathContext} object with a precision setting
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* matching the precision of the IEEE 754-2019 decimal64 format, 16 digits, and a
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* rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}.
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* Note the exponent range of decimal64 is <em>not</em> used for
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* rounding.
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*/
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public static final MathContext DECIMAL64 =
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new MathContext(16, RoundingMode.HALF_EVEN);
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/**
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* A {@code MathContext} object with a precision setting
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* matching the precision of the IEEE 754-2019 decimal128 format, 34 digits, and a
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* rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}.
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* Note the exponent range of decimal64 is <em>not</em> used for
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* rounding.
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*/
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public static final MathContext DECIMAL128 =
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new MathContext(34, RoundingMode.HALF_EVEN);
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/* ----- Shared Properties ----- */
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/**
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* The number of digits to be used for an operation. A value of 0
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* indicates that unlimited precision (as many digits as are
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* required) will be used. Note that leading zeros (in the
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* coefficient of a number) are never significant.
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*
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* <p>{@code precision} will always be non-negative.
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*
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* @serial
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*/
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final int precision;
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/**
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* The rounding algorithm to be used for an operation.
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*
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* @see RoundingMode
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* @serial
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*/
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final RoundingMode roundingMode;
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/* ----- Constructors ----- */
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/**
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* Constructs a new {@code MathContext} with the specified
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* precision and the {@link RoundingMode#HALF_UP HALF_UP} rounding
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* mode.
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*
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* @param setPrecision The non-negative {@code int} precision setting.
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* @throws IllegalArgumentException if the {@code setPrecision} parameter is less
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* than zero.
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*/
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public MathContext(int setPrecision) {
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this(setPrecision, DEFAULT_ROUNDINGMODE);
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return;
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}
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/**
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* Constructs a new {@code MathContext} with a specified
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* precision and rounding mode.
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*
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* @param setPrecision The non-negative {@code int} precision setting.
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* @param setRoundingMode The rounding mode to use.
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* @throws IllegalArgumentException if the {@code setPrecision} parameter is less
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* than zero.
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* @throws NullPointerException if the rounding mode argument is {@code null}
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*/
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public MathContext(int setPrecision,
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RoundingMode setRoundingMode) {
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if (setPrecision < MIN_DIGITS)
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throw new IllegalArgumentException("Digits < 0");
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if (setRoundingMode == null)
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throw new NullPointerException("null RoundingMode");
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precision = setPrecision;
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roundingMode = setRoundingMode;
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return;
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}
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/**
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* Constructs a new {@code MathContext} from a string.
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*
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* The string must be in the same format as that produced by the
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* {@link #toString} method.
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*
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* <p>An {@code IllegalArgumentException} is thrown if the precision
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* section of the string is out of range ({@code < 0}) or the string is
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* not in the format created by the {@link #toString} method.
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*
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* @param val The string to be parsed
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* @throws IllegalArgumentException if the precision section is out of range
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* or of incorrect format
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* @throws NullPointerException if the argument is {@code null}
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*/
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public MathContext(String val) {
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boolean bad = false;
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int setPrecision;
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if (val == null)
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throw new NullPointerException("null String");
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try { // any error here is a string format problem
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if (!val.startsWith("precision=")) throw new RuntimeException();
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int fence = val.indexOf(' '); // could be -1
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int off = 10; // where value starts
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setPrecision = Integer.parseInt(val.substring(10, fence));
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if (!val.startsWith("roundingMode=", fence+1))
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throw new RuntimeException();
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off = fence + 1 + 13;
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String str = val.substring(off, val.length());
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roundingMode = RoundingMode.valueOf(str);
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} catch (RuntimeException re) {
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throw new IllegalArgumentException("bad string format");
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}
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if (setPrecision < MIN_DIGITS)
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throw new IllegalArgumentException("Digits < 0");
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// the other parameters cannot be invalid if we got here
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precision = setPrecision;
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}
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/**
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* Returns the {@code precision} setting.
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* This value is always non-negative.
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*
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* @return an {@code int} which is the value of the {@code precision}
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* setting
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*/
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public int getPrecision() {
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return precision;
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}
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/**
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* Returns the roundingMode setting.
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* This will be one of
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* {@link RoundingMode#CEILING},
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* {@link RoundingMode#DOWN},
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* {@link RoundingMode#FLOOR},
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* {@link RoundingMode#HALF_DOWN},
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* {@link RoundingMode#HALF_EVEN},
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* {@link RoundingMode#HALF_UP},
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* {@link RoundingMode#UNNECESSARY}, or
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* {@link RoundingMode#UP}.
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*
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* @return a {@code RoundingMode} object which is the value of the
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* {@code roundingMode} setting
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*/
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public RoundingMode getRoundingMode() {
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return roundingMode;
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}
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/**
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* Compares this {@code MathContext} with the specified
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* {@code Object} for equality.
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*
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* @param x {@code Object} to which this {@code MathContext} is to
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* be compared.
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* @return {@code true} if and only if the specified {@code Object} is
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* a {@code MathContext} object which has exactly the same
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* settings as this object
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*/
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public boolean equals(Object x){
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if (!(x instanceof MathContext mc))
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return false;
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return mc.precision == this.precision
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&& mc.roundingMode == this.roundingMode; // no need for .equals()
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}
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/**
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* Returns the hash code for this {@code MathContext}.
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*
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* @return hash code for this {@code MathContext}
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*/
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public int hashCode() {
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return this.precision + roundingMode.hashCode() * 59;
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}
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/**
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* Returns the string representation of this {@code MathContext}.
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* The {@code String} returned represents the settings of the
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* {@code MathContext} object as two space-delimited words
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* (separated by a single space character, <code>'\u0020'</code>,
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* and with no leading or trailing white space), as follows:
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* <ol>
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* <li>
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* The string {@code "precision="}, immediately followed
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* by the value of the precision setting as a numeric string as if
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* generated by the {@link Integer#toString(int) Integer.toString}
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* method.
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*
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* <li>
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* The string {@code "roundingMode="}, immediately
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* followed by the value of the {@code roundingMode} setting as a
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* word. This word will be the same as the name of the
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* corresponding public constant in the {@link RoundingMode}
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* enum.
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* </ol>
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* <p>
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* For example:
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* <pre>
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* precision=9 roundingMode=HALF_UP
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* </pre>
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*
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* Additional words may be appended to the result of
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* {@code toString} in the future if more properties are added to
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* this class.
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*
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* @return a {@code String} representing the context settings
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*/
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public java.lang.String toString() {
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return "precision=" + precision + " " +
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"roundingMode=" + roundingMode.toString();
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}
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// Private methods
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/**
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* Reconstitute the {@code MathContext} instance from a stream (that is,
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* deserialize it).
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*
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* @param s the stream being read.
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* @throws IOException if an I/O error occurs
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* @throws ClassNotFoundException if a serialized class cannot be loaded
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*/
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@java.io.Serial
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private void readObject(java.io.ObjectInputStream s)
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throws java.io.IOException, ClassNotFoundException {
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s.defaultReadObject(); // read in all fields
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// validate possibly bad fields
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if (precision < MIN_DIGITS) {
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String message = "MathContext: invalid digits in stream";
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throw new java.io.StreamCorruptedException(message);
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}
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if (roundingMode == null) {
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String message = "MathContext: null roundingMode in stream";
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throw new java.io.StreamCorruptedException(message);
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}
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}
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}
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