MathContext (Java Platform SE 8 )
Keywords: java.math.MathContext class
Date: 2015-11-18

compact1, compact2, compact3
java.math

## Class MathContext

- java.lang.Object
- - java.math.MathContext

- All Implemented Interfaces:
    Serializable

      public final class MathContext
      extends Object
      implements Serializable

  Immutable objects which encapsulate the context settings which describe certain rules for numerical operators, such as those implemented by the `BigDecimal` class.

  The base-independent settings are:

  1. `precision`: the number of digits to be used for an operation; results are rounded to this precision
  2. `roundingMode`: a `RoundingMode` object which specifies the algorithm to be used for rounding.
  Since:
    1.5
  See Also:
    `BigDecimal`, `RoundingMode`, Serialized Form

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static MathContext` | `DECIMAL128` A `MathContext` object with a precision setting matching the IEEE 754R Decimal128 format, 34 digits, and a rounding mode of `HALF_EVEN`, the IEEE 754R default.
    `static MathContext` | `DECIMAL32` A `MathContext` object with a precision setting matching the IEEE 754R Decimal32 format, 7 digits, and a rounding mode of `HALF_EVEN`, the IEEE 754R default.
    `static MathContext` | `DECIMAL64` A `MathContext` object with a precision setting matching the IEEE 754R Decimal64 format, 16 digits, and a rounding mode of `HALF_EVEN`, the IEEE 754R default.
    `static MathContext` | `UNLIMITED` A `MathContext` object whose settings have the values required for unlimited precision arithmetic.

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `MathContext(int setPrecision)` Constructs a new `MathContext` with the specified precision and the `HALF_UP` rounding mode.
    `MathContext(int setPrecision, RoundingMode setRoundingMode)` Constructs a new `MathContext` with a specified precision and rounding mode.
    `MathContext(String val)` Constructs a new `MathContext` from a string.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `equals(Object x)` Compares this `MathContext` with the specified `Object` for equality.
    `int` | `getPrecision()` Returns the `precision` setting.
    `RoundingMode` | `getRoundingMode()` Returns the roundingMode setting.
    `int` | `hashCode()` Returns the hash code for this `MathContext`.
    `String` | `toString()` Returns the string representation of this `MathContext`.

    - ### Methods inherited from class java.lang.Object

      `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- - ### Field Detail

    - #### UNLIMITED

          public static final MathContext UNLIMITED

      A `MathContext` object whose settings have the values required for unlimited precision arithmetic. The values of the settings are: `precision=0 roundingMode=HALF_UP`

    - #### DECIMAL32

          public static final MathContext DECIMAL32

      A `MathContext` object with a precision setting matching the IEEE 754R Decimal32 format, 7 digits, and a rounding mode of `HALF_EVEN`, the IEEE 754R default.

    - #### DECIMAL64

          public static final MathContext DECIMAL64

      A `MathContext` object with a precision setting matching the IEEE 754R Decimal64 format, 16 digits, and a rounding mode of `HALF_EVEN`, the IEEE 754R default.

    - #### DECIMAL128

          public static final MathContext DECIMAL128

      A `MathContext` object with a precision setting matching the IEEE 754R Decimal128 format, 34 digits, and a rounding mode of `HALF_EVEN`, the IEEE 754R default.

  - ### Constructor Detail

    - #### MathContext

          public MathContext(int setPrecision)

      Constructs a new `MathContext` with the specified precision and the `HALF_UP` rounding mode.
      Parameters:
        `setPrecision` - The non-negative `int` precision setting.
      Throws:
        `IllegalArgumentException` - if the `setPrecision` parameter is less than zero.

    - #### MathContext

          public MathContext(int setPrecision,
                             RoundingMode setRoundingMode)

      Constructs a new `MathContext` with a specified precision and rounding mode.
      Parameters:
        `setPrecision` - The non-negative `int` precision setting.
        `setRoundingMode` - The rounding mode to use.
      Throws:
        `IllegalArgumentException` - if the `setPrecision` parameter is less than zero.
        `NullPointerException` - if the rounding mode argument is `null`

    - #### MathContext

          public MathContext(String val)

      Constructs a new `MathContext` from a string. The string must be in the same format as that produced by the `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 `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 `null`

  - ### Method Detail

    - #### getPrecision

          public int getPrecision()

      Returns the `precision` setting. This value is always non-negative.
      Returns:
        an `int` which is the value of the `precision` setting

    - #### getRoundingMode

          public RoundingMode getRoundingMode()

      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`.
      Returns:
        a `RoundingMode` object which is the value of the `roundingMode` setting

    - #### equals

          public boolean equals(Object x)

      Compares this `MathContext` with the specified `Object` for equality.
      Overrides:
        `equals` in class `Object`
      Parameters:
        `x` - `Object` to which this `MathContext` is to be compared.
      Returns:
        `true` if and only if the specified `Object` is a `MathContext` object which has exactly the same settings as this object
      See Also:
        `Object.hashCode()`, `HashMap`

    - #### hashCode

          public int hashCode()

      Returns the hash code for this `MathContext`.
      Overrides:
        `hashCode` in class `Object`
      Returns:
        hash code for this `MathContext`
      See Also:
        `Object.equals(java.lang.Object)`, `System.identityHashCode(java.lang.Object)`

    - #### toString

          public String toString()

      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:
      1. The string `"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 `"roundingMode="`, immediately followed by the value of the `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 `toString` in the future if more properties are added to this class.
      Overrides:
        `toString` in class `Object`
      Returns:
        a `String` representing the context settings

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