{@code precision} will always be non-negative.

serial:

Also see:

RoundingMode
serial:

 public MathContext(int setPrecision) 
{
    /* ----- Constructors ----- */
        this(setPrecision, DEFAULT_ROUNDINGMODE);
        return;
}

Constructs a new {@code MathContext} with the specified precision and the HALF_UP rounding mode.

Parameters:

setPrecision - The non-negative {@code int} precision setting.

Throws:

IllegalArgumentException - if the {@code setPrecision} parameter is less than zero.

 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();
        }
}

Constructs a new {@code MathContext} from a string. The string must be in the same format as that produced by the #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 #toString method.

Parameters:

val - The string to be parsed

Throws:

IllegalArgumentException - if the precision section is out of range or of incorrect format

NullPointerException - if the 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;
        if (precision  > 0 && precision < = MAX_LOOKASIDE) {
            roundingMax = BigInteger.TEN.pow(precision);
            roundingMin = roundingMax.negate();
        }
        roundingMode = setRoundingMode;
        return;
}

Constructs a new {@code MathContext} with a specified precision and rounding mode.

Parameters:

setPrecision - The non-negative {@code int} precision setting.

setRoundingMode - The rounding mode to use.

Throws:

IllegalArgumentException - if the {@code setPrecision} parameter is less than zero.

NullPointerException - if the rounding mode argument is {@code null}

 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()
}

Compares this {@code MathContext} with the specified {@code Object} for equality.

 public int getPrecision() 
{
        return precision;
}

Returns the {@code precision} setting. This value is always non-negative.

 public RoundingMode getRoundingMode() 
{
        return roundingMode;
}

Returns the roundingMode setting. This will be one of RoundingMode#CEILING , RoundingMode#DOWN , RoundingMode#FLOOR , RoundingMode#HALF_DOWN , RoundingMode#HALF_EVEN , RoundingMode#HALF_UP , RoundingMode#UNNECESSARY , or RoundingMode#UP .

 public int hashCode() 
{
        return this.precision + roundingMode.hashCode() * 59;
}

Returns the hash code for this {@code MathContext}.

 public String toString() 
{
        return "precision=" +           precision + " " +
               "roundingMode=" +        roundingMode.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:
1. The string {@code "precision="}, immediately followed by the value of the precision setting as a numeric string as if generated by the Integer.toString method.
2. 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 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.