studenttpar.java

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/**    
  * Copyright (C) 2006, Laboratorio di Valutazione delle Prestazioni - Politecnico di Milano

  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.

  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.

  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  */
  
package jmt.engine.random;

import jmt.common.exception.IncorrectDistributionParameterException;


/**
 *
 * This is the parameter that should be passed to the StudentT
 * distribution.
 *
 * <br><br>Copyright (c) 2003
 * <br>Politecnico di Milano - dipartimento di Elettronica e Informazione
 * @author Fabrizio Frontera - [e-mail]
 *
 */

public class StudentTPar extends Parameter {

	private double freedom;


	/**
	 * It creates a new student T parameter with the provided degrees of freedom.
	 * @param freedom double containing the degrees of freedom of the new student T
	 * distribution. It is defined as double but must be an integer greater than zero.
	 *
	 * @throws IncorrectDistributionParameterException if the degrees of freedom is
	 * not an integer greater than zero.
	 *
	 */
	public StudentTPar(double freedom)
	        throws IncorrectDistributionParameterException {
		if (freedom <= 0 || Math.floor(freedom) != freedom) {
			throw new IncorrectDistributionParameterException("The number of degrees of freedom must be an integer gtz");
		} else {
			this.freedom = freedom;
		}
	}

	public StudentTPar(Double wfreedom)
	        throws IncorrectDistributionParameterException {
		this(wfreedom.doubleValue());
	}

	/**
	 * It verify if the parameter is correct. For the student T distribution,
	 * the value of the degrees of freedom must be an integer greater than zero.
	 *
	 * @return boolean, indicating wether the parameter is correct or not.
	 *
	 */

	public boolean check() {
		return (!(freedom <= 0 || Math.floor(freedom) != freedom));
	}

	/**
	 * It returns the value of the freedom parameter of the student T distribution.
	 * It returns a double but the value is actually an integer.
	 *
	 * @return double with the freedom parameter of the student T distribution.
	 *
	 */

	public double getFreedom() {
		return freedom;
	}

	/**
	 * It allow the user to change the degrees of freedom of the student T distribution.
	 * It verify that the new value is correct (freedom must be an integer
	 * greater than zero).
	 *
	 * @param freedom double indicating the new value of the parameter freedom.
	 *
	 * @throws IncorrectDistributionParameterException if freedom is not an integer
	 * greater than zero.
	 *
	 */

	public void setFreedom(double freedom)
	        throws IncorrectDistributionParameterException {
		this.freedom = freedom;
		if (!check()) {
			throw new IncorrectDistributionParameterException("The number of degrees of freedom must be an integer >0");
		}
	}

} // end StudentTPar