java.math.MathContext Maven / Gradle / Ivy
/*
* 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.
*/
package java.math;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.io.StreamCorruptedException;
/**
* 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 {
private static final long serialVersionUID = 5579720004786848255L;
/**
* A {@code MathContext} which corresponds to the IEEE 754 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 754 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 754 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);
/**
* The number of digits to be used for an operation; results are rounded to
* this precision.
*/
private final int precision;
/**
* A {@code RoundingMode} object which specifies the algorithm to be used
* for rounding.
*/
private final 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) {
this.precision = precision;
this.roundingMode = roundingMode;
checkValid();
}
/**
* 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.
*
* @throws IllegalArgumentException
* if the string is not in the correct format or if the
* precision specified is < 0.
*/
public MathContext(String s) {
int precisionLength = "precision=".length();
int roundingModeLength = "roundingMode=".length();
int spaceIndex;
if (!s.startsWith("precision=") || (spaceIndex = s.indexOf(' ', precisionLength)) == -1) {
throw invalidMathContext("Missing precision", s);
}
String precisionString = s.substring(precisionLength, spaceIndex);
try {
this.precision = Integer.parseInt(precisionString);
} catch (NumberFormatException nfe) {
throw invalidMathContext("Bad precision", s);
}
int roundingModeStart = spaceIndex + 1;
if (!s.regionMatches(roundingModeStart, "roundingMode=", 0, roundingModeLength)) {
throw invalidMathContext("Missing rounding mode", s);
}
roundingModeStart += roundingModeLength;
this.roundingMode = RoundingMode.valueOf(s.substring(roundingModeStart));
checkValid();
}
private IllegalArgumentException invalidMathContext(String reason, String s) {
throw new IllegalArgumentException(reason + ": " + s);
}
private void checkValid() {
if (precision < 0) {
throw new IllegalArgumentException("Negative precision: " + precision);
}
if (roundingMode == null) {
throw new NullPointerException("roundingMode == null");
}
}
/**
* 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.
*
* 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 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 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= roundingMode="
* } where {@code } is an integer describing the number
* of digits used for operations and {@code } is the
* string representation of the rounding mode.
*
* @return a string representation for this {@code MathContext} instance
*/
@Override
public String toString() {
return "precision=" + precision + " roundingMode=" + roundingMode;
}
/**
* Makes checks upon deserialization of a {@code MathContext} instance.
* Checks whether {@code precision >= 0} and {@code roundingMode != null}
*
* @throws StreamCorruptedException
* if {@code precision < 0}
* @throws StreamCorruptedException
* if {@code roundingMode == null}
*/
private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException {
s.defaultReadObject();
try {
checkValid();
} catch (Exception ex) {
throw new StreamCorruptedException(ex.getMessage());
}
}
}