bundles/org.eclipse.uomo.units/src/main/java/org/eclipse/uomo/units/AbstractSystemOfUnits.java

/**
 * Copyright (c) 2005, 2011, Werner Keil and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *    Werner Keil - initial API and implementation
 */
package org.eclipse.uomo.units;

import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

import org.eclipse.uomo.core.IName;
import org.unitsofmeasurement.quantity.Quantity;
import org.unitsofmeasurement.unit.Dimension;
import org.unitsofmeasurement.unit.SystemOfUnits;
import org.unitsofmeasurement.unit.Unit;

/**
 * <p> An abstract base class for unit systems.</p>
 *
 * @author <a href="mailto:uomo@catmedia.us">Werner Keil</a>
 * @version 1.2, $Date: 2011-09-11 14:52:11 +0200 (So, 11 Sep 2011) $
 */
public abstract class AbstractSystemOfUnits implements SystemOfUnits, IName {
	/**
	 * Holds collection of units.
	 */
	protected static final Set<Unit<?>> UNITS = new HashSet<Unit<?>>();

	// ///////////////////
	// Collection View //
	// ///////////////////
	/**
	 * Returns a read only view over the units defined in this class.
	 * 
	 * @return the collection of units.
	 */
	public Set<Unit<?>> getUnits() {
		return Collections.unmodifiableSet(UNITS);
	}
	
	@Override
	public Set<Unit<?>> getUnits(Dimension dimension) {
		return Helper.getUnitsOfDimension(UNITS, dimension);
	}

	@Override
	public <Q extends Quantity<Q>> Unit<Q> getUnit(Class<Q> quantityType) {
		return QuantityFactory.getInstance(quantityType).getMetricUnit();
	}
	
	/**
	 * Adds a new named unit to the collection.
	 * 
	 * @param unit the unit being added.
	 * @param name the name of the unit.
	 * @return <code>unit</code>.
	 */
	@SuppressWarnings("unchecked")
	protected static <U extends Unit<?>> U addUnit(U unit, String name) {
		if (name != null && unit instanceof AbstractUnit) {
			AbstractUnit<?> aUnit = (AbstractUnit<?>)unit;
			aUnit.setName(name);
			UNITS.add(aUnit);
			return (U) aUnit;
		}
		UNITS.add(unit);
		return unit;
	}

	/**
	 * Adds a new unit to the collection.
	 * 
	 * @param unit
	 *            the unit being added.
	 * @return <code>unit</code>.
	 */
	protected static <U extends Unit<?>> U addUnit(U unit) {
		UNITS.add(unit);
		return unit;
	}
	static class Helper {
		static Set<Unit<?>> getUnitsOfDimension(final Set<Unit<?>> units, 
				Dimension dimension) {
			if (dimension != null) {
				Set<Unit<?>>dimSet = new HashSet<Unit<?>>();
				for (Unit<?> u : units) {
					if (dimension.equals(u.getDimension())) {
						dimSet.add(u);
					}
				}
				return dimSet;
			}
			return null;
		}
	}
}