util/src/main/java/org/apache/etch/util/IdGenerator.java

/* $Id$
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.etch.util;

/**
 * Synchronously generates long id numbers.
 */
final public class IdGenerator
{
	/**
	 * Constructs the IdGenerator with the default starting point of 1
	 * and the default stride of 1.
	 */
	public IdGenerator()
	{
		this( 1, 1 );
	}
	
	/**
	 * Constructs the IdGenerator with the specified starting point
	 * and the default stride of 1.
	 *
	 * @param nextId
	 */
	public IdGenerator( long nextId )
	{
		this( nextId, 1 );
	}
	
	/**
	 * Constructs the IdGenerator with the specified starting point
	 * and the specified stride;
	 * @param nextId
	 * @param stride
	 */
	public IdGenerator( long nextId, int stride )
	{
		if (stride <= 0)
			throw new IllegalArgumentException( "stride <= 0" );
		
		this.nextId = nextId;
		this.stride = stride;
	}
	
	private long nextId;
	
	private final int stride;
	
	/**
	 * @return the next id in sequence.
	 */
	public synchronized long next()
	{
		long id = nextId;
		nextId += stride;
		return id;
	}
}