The base-independent settings are: *
{@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; /* ----- 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; 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. * *
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;
}
/**
* 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){
if (!(x instanceof MathContext mc))
return false;
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, '\u0020',
* and with no leading or trailing white space), as follows:
*
* For example: *
* precision=9 roundingMode=HALF_UP
*
*
* 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.
* @throws IOException if an I/O error occurs
* @throws ClassNotFoundException if a serialized class cannot be loaded
*/
@java.io.Serial
private 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);
}
}
}