001    /* MathContext.java -- 
002       Copyright (C) 1999, 2000, 2002, 2004, 2005  Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    
039    package java.math;
040    
041    import java.io.Serializable;
042    
043    /**
044     * Immutable objects describing settings such as rounding mode and digit
045     * precision for numerical operations such as those in the BigDecimal class.
046     * @author Anthony Balkissoon abalkiss at redhat dot com
047     *
048     */
049    public final class MathContext implements Serializable
050    {
051      /** A MathContext for unlimited precision arithmetic * */
052      public static final MathContext UNLIMITED = 
053        new MathContext(0, RoundingMode.HALF_UP);
054      
055      /**
056       * A MathContext for the IEEE 754R Decimal32 format - 7 digit preicision and
057       * HALF_EVEN rounding.
058       */
059      public static final MathContext DECIMAL32 = 
060        new MathContext(7, RoundingMode.HALF_EVEN);
061      
062      /**
063       * A MathContext for the IEEE 754R Decimal64 format - 16 digit preicision and
064       * HALF_EVEN rounding.
065       */
066      public static final MathContext DECIMAL64 = 
067        new MathContext(16, RoundingMode.HALF_EVEN);
068      
069      /**
070       * A MathContext for the IEEE 754R Decimal128 format - 34 digit preicision and
071       * HALF_EVEN rounding.
072       */
073      public static final MathContext DECIMAL128 = 
074        new MathContext(34, RoundingMode.HALF_EVEN);
075      
076      /**
077       * This is the serialVersionUID reported here:
078       * java.sun.com/j2se/1.5.0/docs/api/serialized-form.html#java.math.MathContext
079       */
080      private static final long serialVersionUID = 5579720004786848255L;
081      
082      private int precision;
083      
084      private RoundingMode roundMode;
085      
086      /**
087       * Constructs a new MathContext with the specified precision and with HALF_UP
088       * rounding.
089       * @param setPrecision the precision for the new MathContext
090       * 
091       * @throws IllegalArgumentException if precision is < 0.
092       */
093      public MathContext(int setPrecision)
094      {
095        this(setPrecision, RoundingMode.HALF_UP);
096      }
097      
098      /**
099       * Constructs a new MathContext with the specified precision and rounding
100       * mode.
101       * @param setPrecision the precision
102       * @param setRoundingMode the rounding mode
103       * 
104       * @throws IllegalArgumentException if precision is < 0.
105       */
106      public MathContext(int setPrecision, RoundingMode setRoundingMode)
107      {
108        if (setPrecision < 0)
109          throw new IllegalArgumentException("Precision cannot be less than zero.");
110        precision = setPrecision;
111        roundMode = setRoundingMode;
112      }
113      
114      /**
115       * Constructs a MathContext from a String that has the same form as one
116       * produced by the toString() method.
117       * @param val
118       * 
119       * @throws IllegalArgumentException if the String is not in the correct
120       * format or if the precision specified is < 0.
121       */
122      public MathContext(String val)
123      {
124        try
125        {
126          int roundingModeIndex = val.indexOf("roundingMode", 10);
127          precision = Integer.parseInt(val.substring(10, roundingModeIndex - 1));
128          roundMode = RoundingMode.valueOf(val.substring(roundingModeIndex + 13));
129        }
130        catch (NumberFormatException nfe)
131        {
132          throw new IllegalArgumentException("String not in correct format");
133        }
134        catch (IllegalArgumentException iae)
135        {
136          throw new IllegalArgumentException("String not in correct format");
137        }
138        if (precision < 0)
139          throw new IllegalArgumentException("Precision cannot be less than 0.");
140      }
141      
142      /**
143       * Returns true if x is a MathContext and has the same precision setting
144       * and rounding mode as this MathContext.
145       * 
146       * @return true if the above conditions hold
147       */
148      public boolean equals(Object x)
149      {
150        if (!(x instanceof MathContext))
151          return false;
152        MathContext mc = (MathContext)x;
153        return mc.precision == this.precision
154               && mc.roundMode.equals(this.roundMode);
155      }
156      
157      /**
158       * Returns the precision setting.
159       * @return the precision setting.
160       */
161      public int getPrecision()
162      {
163        return precision;
164      }
165      
166      /**
167       * Returns the rounding mode setting.  This will be one of 
168       * RoundingMode.CEILING, RoundingMode.DOWN, RoundingMode.FLOOR, 
169       * RoundingMode.HALF_DOWN, RoundingMode.HALF_EVEN, RoundingMode.HALF_UP, 
170       * RoundingMode.UNNECESSARY, or RoundingMode.UP.
171       * @return the rounding mode setting.
172       */
173      public RoundingMode getRoundingMode()
174      {
175        return roundMode;
176      }
177      
178      /**
179       * Returns "precision=p roundingMode=MODE" where p is an int giving the 
180       * precision and MODE is UP, DOWN, HALF_UP, HALF_DOWN, HALF_EVEN, CEILING,
181       * FLOOR, or UNNECESSARY corresponding to rounding modes.
182       * 
183       * @return a String describing this MathContext
184       */
185      public String toString()
186      {
187        return "precision="+precision+" roundingMode="+roundMode;
188      }
189      
190      /**
191       * Returns the hashcode for this MathContext.
192       * @return the hashcode for this MathContext.
193       */
194      public int hashCode()
195      {
196        return precision ^ roundMode.hashCode();
197      }
198    }