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