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314 lines
11 KiB
Java
314 lines
11 KiB
Java
/*
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* Copyright 2009 Google Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may not
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* use this file except in compliance with the License. You may obtain a copy of
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* the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations under
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* the License.
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*/
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/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with this
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* work for additional information regarding copyright ownership. The ASF
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* licenses this file to You under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations under
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* the License.
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*
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* INCLUDES MODIFICATIONS BY RICHARD ZSCHECH AS WELL AS GOOGLE.
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*/
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package java.math;
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import java.io.Serializable;
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/**
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* Immutable objects describing settings such as rounding mode and digit
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* precision for the numerical operations provided by class {@link BigDecimal}.
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*/
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public final class MathContext implements Serializable {
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/**
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* A {@code MathContext} which corresponds to the IEEE 754r quadruple decimal
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* precision format: 34 digit precision and {@link RoundingMode#HALF_EVEN}
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* rounding.
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*/
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public static final MathContext DECIMAL128 = new MathContext(34,
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RoundingMode.HALF_EVEN);
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/**
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* A {@code MathContext} which corresponds to the IEEE 754r single decimal
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* precision format: 7 digit precision and {@link RoundingMode#HALF_EVEN}
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* rounding.
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*/
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public static final MathContext DECIMAL32 = new MathContext(7,
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RoundingMode.HALF_EVEN);
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/**
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* A {@code MathContext} which corresponds to the IEEE 754r double decimal
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* precision format: 16 digit precision and {@link RoundingMode#HALF_EVEN}
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* rounding.
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*/
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public static final MathContext DECIMAL64 = new MathContext(16,
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RoundingMode.HALF_EVEN);
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/**
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* A {@code MathContext} for unlimited precision with
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* {@link RoundingMode#HALF_UP} rounding.
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*/
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public static final MathContext UNLIMITED = new MathContext(0,
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RoundingMode.HALF_UP);
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/**
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* An array of {@code char} containing: {@code
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* 'p','r','e','c','i','s','i','o','n','='}. It's used to improve the methods
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* related to {@code String} conversion.
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*
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* @see #MathContext(String)
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* @see #toString()
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*/
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private static final char[] chPrecision = {
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'p', 'r', 'e', 'c', 'i', 's', 'i', 'o', 'n', '='};
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/**
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* An array of {@code char} containing: {@code
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* 'r','o','u','n','d','i','n','g','M','o','d','e','='}. It's used to improve
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* the methods related to {@code String} conversion.
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*
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* @see #MathContext(String)
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* @see #toString()
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*/
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private static final char[] chRoundingMode = {
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'r', 'o', 'u', 'n', 'd', 'i', 'n', 'g', 'M', 'o', 'd', 'e', '='};
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/**
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* This is the serialVersionUID used by the sun implementation.
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*/
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private static final long serialVersionUID = 5579720004786848255L;
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/**
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* The number of digits to be used for an operation; results are rounded to
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* this precision.
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*/
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private int precision;
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/**
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* A {@code RoundingMode} object which specifies the algorithm to be used for
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* rounding.
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*/
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private RoundingMode roundingMode;
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/**
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* Constructs a new {@code MathContext} with the specified precision and with
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* the rounding mode {@link RoundingMode#HALF_UP HALF_UP}. If the precision
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* passed is zero, then this implies that the computations have to be
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* performed exact, the rounding mode in this case is irrelevant.
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*
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* @param precision the precision for the new {@code MathContext}.
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* @throws IllegalArgumentException if {@code precision < 0}.
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*/
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public MathContext(int precision) {
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this(precision, RoundingMode.HALF_UP);
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}
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/**
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* Constructs a new {@code MathContext} with the specified precision and with
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* the specified rounding mode. If the precision passed is zero, then this
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* implies that the computations have to be performed exact, the rounding mode
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* in this case is irrelevant.
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*
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* @param precision the precision for the new {@code MathContext}.
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* @param roundingMode the rounding mode for the new {@code MathContext}.
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* @throws IllegalArgumentException if {@code precision < 0}.
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* @throws NullPointerException if {@code roundingMode} is {@code null}.
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*/
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public MathContext(int precision, RoundingMode roundingMode) {
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if (precision < 0) {
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// math.0C=Digits < 0
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throw new IllegalArgumentException("Digits < 0"); //$NON-NLS-1$
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}
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if (roundingMode == null) {
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// math.0D=null RoundingMode
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throw new NullPointerException("null RoundingMode"); //$NON-NLS-1$
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}
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this.precision = precision;
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this.roundingMode = roundingMode;
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}
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/**
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* Constructs a new {@code MathContext} from a string. The string has to
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* specify the precision and the rounding mode to be used and has to follow
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* the following syntax:
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* "precision=<precision> roundingMode=<roundingMode>" This is the
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* same form as the one returned by the {@link #toString} method.
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*
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* @param val a string describing the precision and rounding mode for the new
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* {@code MathContext}.
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* @throws IllegalArgumentException if the string is not in the correct format
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* or if the precision specified is < 0.
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*/
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public MathContext(String val) {
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if (val == null) {
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throw new NullPointerException("null string");
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}
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char[] charVal = val.toCharArray();
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int i; // Index of charVal
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int j; // Index of chRoundingMode
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int digit; // It will contain the digit parsed
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if ((charVal.length < 27) || (charVal.length > 45)) {
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// math.0E=bad string format
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throw new IllegalArgumentException("bad string format"); //$NON-NLS-1$
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}
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// Parsing "precision=" String
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for (i = 0; (i < chPrecision.length) && (charVal[i] == chPrecision[i]); i++) {
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// empty
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}
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if (i < chPrecision.length) {
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// math.0E=bad string format
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throw new IllegalArgumentException("bad string format"); //$NON-NLS-1$
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}
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// Parsing the value for "precision="...
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digit = Character.digit(charVal[i], 10);
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if (digit == -1) {
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// math.0E=bad string format
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throw new IllegalArgumentException("bad string format"); //$NON-NLS-1$
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}
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this.precision = this.precision * 10 + digit;
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i++;
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do {
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digit = Character.digit(charVal[i], 10);
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if (digit == -1) {
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if (charVal[i] == ' ') {
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// It parsed all the digits
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i++;
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break;
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}
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// It isn't a valid digit, and isn't a white space
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// math.0E=bad string format
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throw new IllegalArgumentException("bad string format"); //$NON-NLS-1$
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}
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// Accumulating the value parsed
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this.precision = this.precision * 10 + digit;
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if (this.precision < 0) {
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// math.0E=bad string format
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throw new IllegalArgumentException("bad string format"); //$NON-NLS-1$
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}
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i++;
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} while (true);
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// Parsing "roundingMode="
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for (j = 0; (j < chRoundingMode.length)
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&& (charVal[i] == chRoundingMode[j]); i++, j++) {
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// empty
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}
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if (j < chRoundingMode.length) {
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// math.0E=bad string format
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throw new IllegalArgumentException("bad string format"); //$NON-NLS-1$
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}
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// Parsing the value for "roundingMode"...
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/*
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* don't use implicit calls to RoundingMode.valueOf here, since it will break
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* if enum name obfuscation is enabled.
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*/
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this.roundingMode = RoundingMode.valueOfExplicit(String.valueOf(charVal, i,
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charVal.length - i));
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}
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/* Public Methods */
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/**
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* Returns true if x is a {@code MathContext} with the same precision setting
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* and the same rounding mode as this {@code MathContext} instance.
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*
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* @param x object to be compared.
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* @return {@code true} if this {@code MathContext} instance is equal to the
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* {@code x} argument; {@code false} otherwise.
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*/
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@Override
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public boolean equals(Object x) {
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return ((x instanceof MathContext)
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&& (((MathContext) x).getPrecision() == precision)
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&& (((MathContext) x).getRoundingMode() == roundingMode));
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}
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/**
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* Returns the precision. The precision is the number of digits used for an
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* operation. Results are rounded to this precision. The precision is
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* guaranteed to be non negative. If the precision is zero, then the
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* computations have to be performed exact, results are not rounded in this
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* case.
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*
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* @return the precision.
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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 rounding mode. The rounding mode is the strategy to be used to
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* round results.
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* <p>
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* The rounding mode is one of {@link RoundingMode#UP},
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* {@link RoundingMode#DOWN}, {@link RoundingMode#CEILING},
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* {@link RoundingMode#FLOOR}, {@link RoundingMode#HALF_UP},
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* {@link RoundingMode#HALF_DOWN}, {@link RoundingMode#HALF_EVEN}, or
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* {@link RoundingMode#UNNECESSARY}.
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*
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* @return the rounding mode.
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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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* Returns the hash code for this {@code MathContext} instance.
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*
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* @return the hash code for this {@code MathContext}.
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*/
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@Override
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public int hashCode() {
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// Make place for the necessary bits to represent 8 rounding modes
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return ((precision << 3) | roundingMode.ordinal());
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}
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/**
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* Returns the string representation for this {@code MathContext} instance.
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* The string has the form {@code
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* "precision=<precision> roundingMode=<roundingMode>" * } where
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* {@code <precision>} is an integer describing the number of digits
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* used for operations and {@code <roundingMode>} is the string
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* representation of the rounding mode.
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*
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* @return a string representation for this {@code MathContext} instance
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*/
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@Override
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public String toString() {
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StringBuilder sb = new StringBuilder(45);
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sb.append(chPrecision);
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sb.append(precision);
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sb.append(' ');
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sb.append(chRoundingMode);
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sb.append(roundingMode);
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return sb.toString();
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}
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}
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