SICoefficients.java
package org.djunits.unit;
import java.util.EnumMap;
/**
* <p>
* Copyright (c) 2015-2018 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
* BSD-style license. See <a href="http://djunits.org/docs/license.html">DJUNITS License</a>.
* <p>
* $LastChangedDate: 2018-01-28 03:17:44 +0100 (Sun, 28 Jan 2018) $, @version $Revision: 256 $, by $Author: averbraeck $,
* initial version Jun 15, 2014 <br>
* @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
*/
public class SICoefficients
{
/** the map with SI base units and corresponding coefficients. */
private final EnumMap<SI, Integer> coefficientsMap;
/**
* Construct an instance of SICoefficients.
* @param coefficients the map with SI base units and corresponding coefficients
*/
protected SICoefficients(final EnumMap<SI, Integer> coefficients)
{
this.coefficientsMap = coefficients;
}
/** {@inheritDoc} */
@Override
public final String toString()
{
return enumMapToString(this.coefficientsMap);
}
/**
* Convert an enumMap of coefficient to the normalized string representation.
* @param map EnumMap<{@link SI}, Integer>; the EnumMap
* @return String
*/
protected static String enumMapToString(final EnumMap<SI, Integer> map)
{
StringBuffer result = new StringBuffer();
for (SI si : map.keySet())
{
if (map.get(si) > 0)
{
result.append(si.name());
if (map.get(si) != 1)
{
result.append(map.get(si));
}
}
}
if (result.length() == 0)
{
result.append("1");
}
boolean first = true;
for (SI si : map.keySet())
{
if (map.get(si) < 0)
{
if (first)
{
result.append("/");
first = false;
}
result.append(si.name());
if (map.get(si) != -1)
{
result.append(-map.get(si));
}
}
}
return result.toString();
}
/**
* @return coefficientsMap
*/
public final EnumMap<SI, Integer> getCoefficientsMap()
{
return this.coefficientsMap;
}
/**
* Convert a coefficient string to <i>standard format</i>.
* @param coefficientString String; the string to convert
* @return String; the normalized coefficient string
* @throws UnitException when the coefficientString could not be parsed
*/
public static String normalize(final String coefficientString) throws UnitException
{
return enumMapToString(parse(coefficientString));
}
/**
* @param coefficientString such as kgm/s2 or kg-2m^3/s2A or Kmmol3/Askcd4 or mol. <br>
* The grammar of a coefficientString is:<br>
* <table summary="">
* <tr>
* <td>coefficientString</td>
* <td>::=</td>
* <td><empty> | [ 1 | powerString ] | [ '1 /' powerString ]</td>
* </tr>
* <tr>
* <td>powerString</td>
* <td>::=</td>
* <td>unitName [ [ ^ ] integer ] [ [ dotOrSlash ] powerString ]</td>
* </tr>
* <tr>
* <td>dotOrSlash</td>
* <td>::=</td>
* <td>. | /</td>
* </tr>
* <tr>
* <td>unitName</td>
* <td>::=</td>
* <td>kg | m | s | A | K | cd | mol</td>
* </tr>
* </table>
* <br>
* White space can appear anywhere in a coefficientString. <br>
* If "integer" does not fit in an Integer, the resulting coefficient will be very wrong.
* @return an instance of SICoefficients
* @throws UnitException if the coefficientString is not parsable.
*/
public static EnumMap<SI, Integer> parse(final String coefficientString) throws UnitException
{
// System.out.println("coefficientString is \"" + coefficientString + "\"");
EnumMap<SI, Integer> coefficients = new EnumMap<SI, Integer>(SI.class);
String cs = coefficientString;
cs = cs.replace(".", "").replace(" ", "");
if (cs.equals("1")) // This is a special case...
{
return coefficients;
}
if (cs.startsWith("1/"))
{
cs = cs.substring(1); // remove the leading "1"
}
int factor = 1;
while (cs.length() > 0)
{
if (cs.startsWith("/"))
{
cs = cs.substring(1);
if (cs.length() < 1)
{
throw new UnitException("No SI name after slash in " + coefficientString);
}
factor = -1;
}
boolean parsedPowerString = false;
int factor2 = 1;
for (SI si : SI.values())
{
factor2 = 1;
String name = si.name();
if (!cs.startsWith(name))
{
continue;
}
int endPos = name.length();
if (cs.substring(endPos).startsWith("ol"))
{
continue; // Don't confuse "m" (for meter) and "mol"
}
// Found the unit name
if (cs.substring(endPos).startsWith("^"))
{
endPos++;
}
int value = 1;
int digitsSeen = 0;
if (cs.substring(endPos).startsWith("-"))
{
factor2 = -1;
endPos++;
}
while (cs.length() > endPos)
{
char digit = cs.charAt(endPos);
if (digit >= '0' && digit <= '9')
{
if (0 == digitsSeen)
{
value = 0;
}
value = value * 10 + digit - '0';
endPos++;
digitsSeen++;
}
else
{
break;
}
}
Integer oldValue = coefficients.get(si);
if (null == oldValue)
{
oldValue = 0;
}
coefficients.put(si, oldValue + value * factor * factor2);
parsedPowerString = true;
cs = cs.substring(endPos);
break;
}
if (!parsedPowerString)
{
throw new UnitException("Not an SI unit name in \"" + coefficientString + "\" at \"" + cs + "\"");
}
}
return coefficients;
}
/**
* @param a the first set of coefficients
* @param b the second set of coefficients
* @return the coefficients of a*b (coefficients are added)
*/
public static SICoefficients multiply(final SICoefficients a, final SICoefficients b)
{
EnumMap<SI, Integer> coefficients = new EnumMap<SI, Integer>(SI.class);
for (SI si : a.getCoefficientsMap().keySet())
{
coefficients.put(si, a.getCoefficientsMap().get(si));
}
for (SI si : b.getCoefficientsMap().keySet())
{
if (coefficients.containsKey(si))
{
coefficients.put(si, coefficients.get(si) + b.getCoefficientsMap().get(si));
}
else
{
coefficients.put(si, b.getCoefficientsMap().get(si));
}
}
for (SI si : coefficients.keySet())
{
if (coefficients.get(si) == 0)
{
coefficients.remove(si);
}
}
return new SICoefficients(coefficients);
}
/**
* @param a the first set of coefficients
* @param b the second set of coefficients
* @return the coefficients of a/b (coefficients are subtracted)
*/
public static SICoefficients divide(final SICoefficients a, final SICoefficients b)
{
EnumMap<SI, Integer> coefficients = new EnumMap<SI, Integer>(SI.class);
for (SI si : a.getCoefficientsMap().keySet())
{
coefficients.put(si, a.getCoefficientsMap().get(si));
}
for (SI si : b.getCoefficientsMap().keySet())
{
if (coefficients.containsKey(si))
{
coefficients.put(si, coefficients.get(si) - b.getCoefficientsMap().get(si));
}
else
{
coefficients.put(si, -b.getCoefficientsMap().get(si));
}
}
for (SI si : coefficients.keySet())
{
if (coefficients.get(si) == 0)
{
coefficients.remove(si);
}
}
return new SICoefficients(coefficients);
}
}