The base-independent settings are: *
* precision=0 roundingMode=HALF_UP
*
*/
public static final MathContext UNLIMITED =
new MathContext(0, RoundingMode.HALF_UP);
/**
* A MathContext object with a precision setting
* matching the IEEE 754R Decimal32 format, 7 digits, and a
* rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}, the
* IEEE 754R default.
*/
public static final MathContext DECIMAL32 =
new MathContext(7, RoundingMode.HALF_EVEN);
/**
* A MathContext object with a precision setting
* matching the IEEE 754R Decimal64 format, 16 digits, and a
* rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}, the
* IEEE 754R default.
*/
public static final MathContext DECIMAL64 =
new MathContext(16, RoundingMode.HALF_EVEN);
/**
* A MathContext object with a precision setting
* matching the IEEE 754R Decimal128 format, 34 digits, and a
* rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}, the
* IEEE 754R default.
*/
public static final MathContext DECIMAL128 =
new MathContext(34, RoundingMode.HALF_EVEN);
/* ----- Shared Properties ----- */
/**
* The number of digits to be used for an operation. A value of 0
* indicates that unlimited precision (as many digits as are
* required) will be used. Note that leading zeros (in the
* coefficient of a number) are never significant.
*
* 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; /** * Lookaside for the rounding points (the numbers which determine * whether the coefficient of a number will require rounding). * These will be present if precision>0 and * precision<=MAX_LOOKASIDE. In this case they will share the * BigInteger int[] array. Note that the transients * cannot be final because they are reconstructed on * deserialization. */ transient BigInteger roundingMax = null; transient BigInteger roundingMin = null; private static final int MAX_LOOKASIDE = 1000; /* ----- Constructors ----- */ /** * Constructs a new MathContext with the specified * precision and the {@link RoundingMode#HALF_UP HALF_UP} rounding * mode. * * @param setPrecision The non-negative int precision setting. * @throws IllegalArgumentException setPrecision parameter less * than zero. */ public MathContext(int setPrecision) { this(setPrecision, DEFAULT_ROUNDINGMODE); return; } /** * Constructs a new MathContext with a specified * precision and rounding mode. * * @param setPrecision The non-negative int precision setting. * @param setRoundingMode The rounding mode to use. * @throws IllegalArgumentException setPrecision parameter less * than zero. */ 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; if (precision > 0 && precision <= MAX_LOOKASIDE) { roundingMax = BigInteger.TEN.pow(precision); roundingMin = roundingMax.negate(); } roundingMode = setRoundingMode; return; } /** * Constructs a new MathContext from a string. * * The string must be in the same format as that produced by the * {@link #toString} method. * *
An IllegalArgumentException is thrown if the precision * section of the string is out of range (< 0) or the string is * not in the format created by the {@link #toString} method. * * @param val The string to be parsed * @throws IllegalArgumentException precision parameter out of range * or incorrect format */ 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; if (precision > 0 && precision <= MAX_LOOKASIDE) { roundingMax = BigInteger.TEN.pow(precision); roundingMin = roundingMax.negate(); } } /** * Returns the precision setting. * This value is always non-negative. * * @return an int which is the value of the 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 RoundingMode object which is the value of the * roundingMode setting */ public RoundingMode getRoundingMode() { return roundingMode; } /** * Compares this MathContext with the specified * Object for equality. * * @param x Object to which this MathContext is to * be compared. * @return true if and only if the specified Object is * a MathContext object which has exactly the same * settings as this object. */ public boolean equals(Object x){ MathContext mc; if (!(x instanceof MathContext)) return false; mc = (MathContext) x; return mc.precision == this.precision && mc.roundingMode == this.roundingMode; // no need for .equals() } /** * Returns the hash code for this MathContext. * * @return hash code for this MathContext */ public int hashCode() { return this.precision + roundingMode.hashCode() * 59; } /** * Returns the string representation of this MathContext. * The String returned represents the settings of the * 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
* toString in the future if more properties are added to
* this class.
*
* @return a String representing the context settings.
*/
public java.lang.String toString() {
return "precision=" + precision + " " +
"roundingMode=" + roundingMode.toString();
}
// Private methods
/**
* Reconstitute the MathContext instance from a stream (that is,
* deserialize it).
*
* @param s the stream being read.
*/
private synchronized 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);
}
// Set the lookaside, if applicable
if (precision <= MAX_LOOKASIDE) {
roundingMax = BigInteger.TEN.pow(precision);
roundingMin = roundingMax.negate();
}
}
}