/*
 * 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 default unit database.
 * 
 * @author Steven R. Emmerson
 */
public final class UnitDBManager implements Serializable {
	private static final long	serialVersionUID	= 1L;
	/**
	 * The singleton instance of the default unit database.
	 * 
	 * @serial
	 */
	private static UnitDB		instance;

	/**
	 * Gets the default unit database.
	 * 
	 * @return The default unit database.
	 * @throws UnitDBException
	 *             The default unit database couldn't be created.
	 */
	public static synchronized UnitDB instance() throws UnitDBException {
			if (instance == null) {
				instance = StandardUnitDB.instance();
			}
		return instance;
	}

	/**
	 * Sets the default unit database. You'd better know what you're doing if
	 * you call this method!
	 * 
	 * @param instance
	 *            The unit database to be made the default one.
	 */
	public static synchronized void setInstance(final UnitDB instance) {
		UnitDBManager.instance = instance;
	}
}