UniformGenerator.java

/**                                                                                                                                                                                
 * Copyright (c) 2010 Yahoo! Inc. All rights reserved.                                                                                                                             
 *                                                                                                                                                                                 
 * Licensed 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. See accompanying                                                                                                                 
 * LICENSE file.                                                                                                                                                                   
 */

package com.yahoo.ycsb.generator;

import java.util.Vector;

/**
 * An expression that generates a random integer in the specified range
 */
public class UniformGenerator extends Generator
{
	
	Vector<String> _values;
	String _laststring;
	UniformIntegerGenerator _gen;
	

	/**
	 * Creates a generator that will return strings from the specified set uniformly randomly
	 */
	@SuppressWarnings( "unchecked" ) 
	public UniformGenerator(Vector<String> values)
	{
		_values=(Vector<String>)values.clone();
		_laststring=null;
		_gen=new UniformIntegerGenerator(0,values.size()-1);
	}

	/**
	 * Generate the next string in the distribution.
	 */
	public String nextString()
	{
		_laststring=_values.elementAt(_gen.nextInt());
		return _laststring;
	}
	
	/**
	 * Return the previous string generated by the distribution; e.g., returned from the last nextString() call. 
	 * Calling lastString() should not advance the distribution or have any side effects. If nextString() has not yet 
	 * been called, lastString() should return something reasonable.
	 */
	public String lastString()
	{
		if (_laststring==null)
		{
			nextString();
		}
		return _laststring;
	}
}