/*
* Copyright 1998-2014 University Corporation for Atmospheric Research/Unidata
*
* Portions of this software were developed by the Unidata Program at the
* University Corporation for Atmospheric Research.
*
* Access and use of this software shall impose the following obligations
* and understandings on the user. The user is granted the right, without
* any fee or cost, to use, copy, modify, alter, enhance and distribute
* this software, and any derivative works thereof, and its supporting
* documentation for any purpose whatsoever, provided that this entire
* notice appears in all copies of the software, derivative works and
* supporting documentation. Further, UCAR requests that the user credit
* UCAR/Unidata in any publications that result from the use of this
* software or in any product that includes this software. The names UCAR
* and/or Unidata, however, may not be used in any advertising or publicity
* to endorse or promote any products or commercial entity unless specific
* written permission is obtained from UCAR/Unidata. The user also
* understands that UCAR/Unidata is not obligated to provide the user with
* any support, consulting, training or assistance of any kind with regard
* to the use, operation and performance of this software nor to provide
* the user with any updates, revisions, new versions or "bug fixes."
*
* THIS SOFTWARE IS PROVIDED BY UCAR/UNIDATA "AS IS" AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL UCAR/UNIDATA BE LIABLE FOR ANY SPECIAL,
* INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
* FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
* NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
* WITH THE ACCESS, USE OR PERFORMANCE OF THIS SOFTWARE.
*/
package ucar.units;
import java.io.Serializable;
/**
* Provides support for managing a UnitSystem.
*
* @author Steven R. Emmerson
*/
public final class UnitSystemManager implements Serializable {
private static final long serialVersionUID = 1L;
/**
* The singleton instance of the system of units.
*
* @serial
*/
private static UnitSystem instance;
/**
* Returns an instance of the system of units.
*
* @return An instance of the system of units.
*/
public static synchronized UnitSystem instance() throws UnitSystemException {
if (instance == null) {
instance = SI.instance();
}
return instance;
}
/**
* Sets the system of units. This must be called before any call to
* <code>instance()</code>.
*
* @param instance
* The system of units.
* @throws UnitSystemException
* <code>instance()</code> was called earlier.
*/
public static synchronized void setInstance(final UnitSystem instance)
throws UnitSystemException {
if (instance != null) {
throw new UnitSystemException("Unit system already used");
}
UnitSystemManager.instance = instance;
}
}