MathContext.java

/* MathContext.java --
   Copyright (C) 1999, 2000, 2002, 2004, 2005  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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General Public License for more details.

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02110-1301 USA.

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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
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this exception to your version of the library, but you are not
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package java.math;

import java.io.Serializable;

/**
 * Immutable objects describing settings such as rounding mode and digit
 * precision for numerical operations such as those in the BigDecimal class.
 * @author Anthony Balkissoon abalkiss at redhat dot com
 *
 */
public final class MathContext implements Serializable
{
  /** A MathContext for unlimited precision arithmetic * */
  public static final MathContext UNLIMITED =
    new MathContext(0, RoundingMode.HALF_UP);

  /**
   * A MathContext for the IEEE 754R Decimal32 format - 7 digit preicision and
   * HALF_EVEN rounding.
   */
  public static final MathContext DECIMAL32 =
    new MathContext(7, RoundingMode.HALF_EVEN);

  /**
   * A MathContext for the IEEE 754R Decimal64 format - 16 digit preicision and
   * HALF_EVEN rounding.
   */
  public static final MathContext DECIMAL64 =
    new MathContext(16, RoundingMode.HALF_EVEN);

  /**
   * A MathContext for the IEEE 754R Decimal128 format - 34 digit preicision and
   * HALF_EVEN rounding.
   */
  public static final MathContext DECIMAL128 =
    new MathContext(34, RoundingMode.HALF_EVEN);

  /**
   * This is the serialVersionUID reported here:
   * java.sun.com/j2se/1.5.0/docs/api/serialized-form.html#java.math.MathContext
   */
  private static final long serialVersionUID = 5579720004786848255L;

  private int precision;

  private RoundingMode roundMode;

  /**
   * Constructs a new MathContext with the specified precision and with HALF_UP
   * rounding.
   * @param setPrecision the precision for the new MathContext
   *
   * @throws IllegalArgumentException if precision is < 0.
   */
  public MathContext(int setPrecision)
  {
    this(setPrecision, RoundingMode.HALF_UP);
  }

  /**
   * Constructs a new MathContext with the specified precision and rounding
   * mode.
   * @param setPrecision the precision
   * @param setRoundingMode the rounding mode
   *
   * @throws IllegalArgumentException if precision is < 0.
   */
  public MathContext(int setPrecision, RoundingMode setRoundingMode)
  {
    if (setPrecision < 0)
      throw new IllegalArgumentException("Precision cannot be less than zero.");
    precision = setPrecision;
    roundMode = setRoundingMode;
  }

  /**
   * Constructs a MathContext from a String that has the same form as one
   * produced by the toString() method.
   * @param val
   *
   * @throws IllegalArgumentException if the String is not in the correct
   * format or if the precision specified is < 0.
   */
  public MathContext(String val)
  {
    try
    {
      int roundingModeIndex = val.indexOf("roundingMode", 10);
      precision = Integer.parseInt(val.substring(10, roundingModeIndex - 1));
      roundMode = RoundingMode.valueOf(val.substring(roundingModeIndex + 13));
    }
    catch (NumberFormatException nfe)
    {
      throw new IllegalArgumentException("String not in correct format");
    }
    catch (IllegalArgumentException iae)
    {
      throw new IllegalArgumentException("String not in correct format");
    }
    if (precision < 0)
      throw new IllegalArgumentException("Precision cannot be less than 0.");
  }

  /**
   * Returns true if x is a MathContext and has the same precision setting
   * and rounding mode as this MathContext.
   *
   * @return true if the above conditions hold
   */
  public boolean equals(Object x)
  {
    if (!(x instanceof MathContext))
      return false;
    MathContext mc = (MathContext)x;
    return mc.precision == this.precision
           && mc.roundMode.equals(this.roundMode);
  }

  /**
   * Returns the precision setting.
   * @return the precision setting.
   */
  public int getPrecision()
  {
    return precision;
  }

  /**
   * Returns the rounding mode 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.
   * @return the rounding mode setting.
   */
  public RoundingMode getRoundingMode()
  {
    return roundMode;
  }

  /**
   * Returns "precision=p roundingMode=MODE" where p is an int giving the
   * precision and MODE is UP, DOWN, HALF_UP, HALF_DOWN, HALF_EVEN, CEILING,
   * FLOOR, or UNNECESSARY corresponding to rounding modes.
   *
   * @return a String describing this MathContext
   */
  public String toString()
  {
    return "precision="+precision+" roundingMode="+roundMode;
  }

  /**
   * Returns the hashcode for this MathContext.
   * @return the hashcode for this MathContext.
   */
  public int hashCode()
  {
    return precision ^ roundMode.hashCode();
  }
}