File	Doc	Category	Size	Date	Package
MathContext.java	API Doc	Java SE 6 API	11688	Tue Jun 10 00:25:40 BST 2008	java.math

MathContext

• java.lang.Object

Fields Summary
private static final int	DEFAULT_DIGITS
private static final RoundingMode	DEFAULT_ROUNDINGMODE
private static final int	MIN_DIGITS
private static final long	serialVersionUID
public static final MathContext	UNLIMITED A {@code MathContext} object whose settings have the values required for unlimited precision arithmetic. The values of the settings are: precision=0 roundingMode=HALF_UP
public static final MathContext	DECIMAL32 A {@code 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	DECIMAL64 A {@code 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	DECIMAL128 A {@code 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.
final int	precision 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. {@code precision} will always be non-negative.
final RoundingMode	roundingMode The rounding algorithm to be used for an operation.
transient BigInteger	roundingMax Lookaside for the rounding points (the numbers which determine whether the coefficient of a number will require rounding). These will be present if {@code precision > 0} and {@code precision <= MAX_LOOKASIDE}. In this case they will share the {@code BigInteger int[]} array. Note that the transients cannot be {@code final} because they are reconstructed on deserialization.
transient BigInteger	roundingMin
private static final int	MAX_LOOKASIDE

Constructors Summary
public MathContext(int setPrecision) 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. /* ----- Constructors ----- */ this(setPrecision, DEFAULT_ROUNDINGMODE); return;
public MathContext(int setPrecision, RoundingMode setRoundingMode) 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} 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;
public MathContext(String val) 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} 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(); }

Methods Summary
public boolean	equals(java.lang.Object x) 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 MathContext mc; if (!(x instanceof MathContext)) return false; mc = (MathContext) x; return mc.precision == this.precision && mc.roundingMode == this.roundingMode; // no need for .equals()
public int	getPrecision() Returns the {@code precision} setting. This value is always non-negative. return an {@code int} which is the value of the {@code precision} setting return precision;
public java.math.RoundingMode	getRoundingMode() 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 return roundingMode;
public int	hashCode() Returns the hash code for this {@code MathContext}. return hash code for this {@code MathContext} return this.precision + roundingMode.hashCode() * 59;
private synchronized void	readObject(java.io.ObjectInputStream s) Reconstitute the {@code MathContext} instance from a stream (that is, deserialize it). param s the stream being read. 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(); }
public java.lang.String	toString() 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: The string {@code "precision="}, immediately followed by the value of the precision setting as a numeric string as if generated by the {@link Integer#toString(int) Integer.toString} method. The string {@code "roundingMode="}, immediately followed by the value of the {@code roundingMode} setting as a word. This word will be the same as the name of the corresponding public constant in the {@link RoundingMode} enum. 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 return "precision=" + precision + " " + "roundingMode=" + roundingMode.toString();