/*
* Copyright 1998, University Corporation for Atmospheric Research
* See file LICENSE for copying and redistribution conditions.
*
* $Id: UnitTable.java,v 1.6 2009-04-21 20:15:10 steve Exp $
*/
package visad.data.units;
import java.util.Collections;
import java.util.Comparator;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.SortedSet;
import java.util.TreeSet;
import visad.BaseUnit;
import visad.DerivedUnit;
import visad.OffsetUnit;
import visad.SI;
import visad.ScaledUnit;
import visad.Unit;
/**
* Provides support for a table of units.
*
* @author Steven R. Emmerson
*/
public class
UnitTable
implements UnitsDB, java.io.Serializable
{
private static final long serialVersionUID = 1L;
/**
* Name-to-unit map.
* @serial
*/
private final Hashtable nameMap;
/**
* Symbol-to-unit map.
* @serial
*/
private final Hashtable symbolMap;
/**
* The unit set.
* @serial
*/
private final SortedSet unitSet;
/**
* Construct.
*
* @param numNames Anticipated minimum number of names in the
* database.
* @throws IllegalArgumentException numNames < 0.
*/
public
UnitTable(int numNames)
throws IllegalArgumentException
{
this(numNames, 0);
}
/**
* Construct.
*
* @param numNames Anticipated minimum number of names in the
* database.
* @param numSymbols Anticipated minimum number of symbols in the
* database.
* @throws IllegalArgumentException numNames < 0 || numSymbols < 0
* .
*/
public
UnitTable(int numNames, int numSymbols)
throws IllegalArgumentException
{
if (numNames < 0 || numSymbols < 0)
throw new IllegalArgumentException("Negative hashtable size");
nameMap = new Hashtable(numNames);
symbolMap = new Hashtable(numSymbols);
unitSet =
Collections.synchronizedSortedSet(
new TreeSet(
new Comparator()
{
public int
compare(Object o1, Object o2)
{
return ((Unit)o1).toString().compareToIgnoreCase(
((Unit)o2).toString());
}
}));
}
/**
* Get a unit.
*
* @param name The exact name of the unit to be retrieved. If it is
* the empty string, then the dimensionless, unity
* unit
* will be returned.
* @return The unit of the matching entry or null if not found.
* @require name is non-null.
*/
public Unit
get(String name)
{
Unit unit = null; // default
if (name.length() == 0)
{
// Return a unity, dimensionless unit.
unit = new DerivedUnit();
}
else
{
/*
* Try the symbol table first because symbols are case-sensitive.
*/
unit = getBySymbol(name);
if (unit == null)
unit = getByName(name);
}
return unit;
}
/**
* Get a unit by name.
*
* @param name The name of the unit to be retrieved. If it is
* the empty string, then the dimensionless, unity
* unit
* will be returned.
* @return The unit of the matching entry or null if not found.
* @require name is non-null.
*/
protected Unit
getByName(String name)
{
return (Unit)nameMap.get(name.toLowerCase());
}
/**
* Get a unit by symbol.
*
* @param symbol The exact symbol of the unit to be retrieved. If it is
* the empty string, then the dimensionless, unity
* unit
* will be returned.
* @return The unit of the matching entry or null if not found.
* @require name is non-null.
*/
protected Unit
getBySymbol(String symbol)
{
return (Unit)symbolMap.get(symbol);
}
/**
* Adds a base unit.
*
* @param unit The base unit to be added.
* @throws IllegalArgumentException
* The base unit argument is invalid.
*/
public void
put(BaseUnit unit)
throws IllegalArgumentException
{
String name = unit.unitName();
putName(name, unit);
putName(makePlural(name), unit);
putSymbol(unit.unitSymbol(), unit);
}
/**
* Returns the plural form of a name. Regular rules are used to generate
* the plural form.
* @param name The name.
* @return The plural form of the name.
*/
protected String
makePlural(String name)
{
String plural;
int length = name.length();
char lastChar = name.charAt(length-1);
if (lastChar != 'y')
{
plural = name +
(lastChar == 's' || lastChar == 'x' ||
lastChar == 'z' || name.endsWith("ch")
? "es"
: "s");
}
else
{
if (length == 1)
{
plural = name + "s";
}
else
{
char penultimateChar = name.charAt(length-2);
plural =
(penultimateChar == 'a' || penultimateChar == 'e' ||
penultimateChar == 'i' || penultimateChar == 'o' ||
penultimateChar == 'u')
? name + "s"
: name.substring(0, length-1) + "ies";
}
}
return plural;
}
/**
* Adds a name and a unit to the name table.
* @param name The name to be added.
* @param unit The unit to be added.
* @throws IllegalArgumentException Invalid argument.
*/
public void
putName(String name, Unit unit)
{
if (name == null)
throw new IllegalArgumentException(this.getClass().getName() +
".putName(String,Unit): unit name");
if (unit == null)
throw new IllegalArgumentException(this.getClass().getName() +
".putName(String,Unit): unit");
name = name.toLowerCase();
String[] names =
(name.indexOf(' ') == -1 && name.indexOf('_') == -1)
? new String[] {name}
: new String[] {
name.replace('_', ' '),
name.replace(' ', '_')};
for (int i = 0; i < names.length; i++)
{
Unit prevUnit = (Unit)nameMap.get(names[i]);
if (prevUnit != null && !prevUnit.equals(unit))
throw new IllegalArgumentException(
"Attempt to replace unit \"" + prevUnit + " with unit \"" +
unit + '"');
nameMap.put(names[i], unit);
}
unitSet.add(unit);
}
/**
* Adds a symbol and a unit to the symbol table.
* @param symbol The symbol to be added.
* @param unit The unit to be added.
* @throws IllegalArgumentException Invalid argument.
*/
public void
putSymbol(String symbol, Unit unit)
{
if (symbol == null)
throw new IllegalArgumentException(this.getClass().getName() +
".putName(String,Unit): unit symbol");
if (unit == null)
throw new IllegalArgumentException(this.getClass().getName() +
".putName(String,Unit): unit");
Unit prevUnit = (Unit)symbolMap.get(symbol);
if (prevUnit != null && !prevUnit.equals(unit))
throw new IllegalArgumentException(
"Attempt to replace unit \"" + prevUnit + " with unit \"" +
unit + '"');
symbolMap.put(symbol, unit);
unitSet.add(unit);
}
/**
* Get an enumeration of the unit names in the table. The Object returned
* by nextElement() is a String.
*/
public Enumeration
getNameEnumeration()
{
return nameMap.keys();
}
/**
* Get an enumeration of the unit symbols in the table. The Object returned
* by nextElement() is a String.
*/
public Enumeration
getSymbolEnumeration()
{
return symbolMap.keys();
}
/**
* Get an enumeration of the units in the table. The Object returned
* by nextElement() is a Unit.
*/
public Enumeration
getUnitEnumeration()
{
return new Enumeration()
{
private final Iterator iter = unitSet.iterator();
public boolean hasMoreElements()
{
return iter.hasNext();
}
public Object nextElement()
{
return iter.next();
}
};
}
/**
* Return a string representation of this instance.
*/
public String
toString()
{
return nameMap.toString() + symbolMap.toString();
}
/**
* Test this class.
* @exception java.lang.Exception A problem occurred.
*/
public static void main(String[] args)
throws Exception
{
UnitTable db = new UnitTable(13);
db.put(SI.ampere);
db.put(SI.candela);
db.put(SI.kelvin);
db.put(SI.kilogram);
db.put(SI.meter);
db.put(SI.mole);
db.put(SI.second);
db.put(SI.radian);
db.putName("amp", SI.ampere); // alias
db.putName("celsius", new OffsetUnit(273.15, SI.kelvin));
db.putName("newton",
SI.kilogram.multiply(SI.meter).divide(SI.second.pow(2)));
db.putName("rankine", new ScaledUnit(1/1.8, SI.kelvin));
db.putName("fahrenheit",
new OffsetUnit(459.67, (ScaledUnit)db.get("rankine")));
System.out.println("db:");
System.out.println(db.toString());
}
/**
* List the units in the database.
*/
public void
list()
{
Enumeration en = getUnitEnumeration();
while (en.hasMoreElements())
{
Unit unit = (Unit)en.nextElement();
System.out.println(unit.getIdentifier() + " = " +
unit.getDefinition());
}
}
}
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