/* ===========================================================

 * JFreeChart : a free chart library for the Java(tm) platform

 * ===========================================================

 *

 * (C) Copyright 2000-2004, by Object Refinery Limited and Contributors.

 *

 * Project Info:  http://www.jfree.org/jfreechart/index.html

 *

 * This library is free software; you can redistribute it and/or modify it under the terms

 * of the GNU Lesser General Public License as published by the Free Software Foundation;

 * either version 2.1 of the License, or (at your option) any later version.

 *

 * This library 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 Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License along with this

 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,

 * Boston, MA 02111-1307, USA.

 *

 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 

 * in the United States and other countries.]

 *

 * ---------------------

 * SimpleTimePeriod.java

 * ---------------------

 * (C) Copyright 2002, 2003 by Object Refinery Limited and Contributors.

 *

 * Original Author:  David Gilbert (for Object Refinery Limited);

 * Contributor(s):   -;

 *

 * $Id: SimpleTimePeriod.java,v 1.1 2004/08/31 15:34:17 mungady Exp $

 *

 * Changes

 * -------

 * 07-Oct-2002 : Added Javadocs (DG);

 * 10-Jan-2003 : Renamed TimeAllocation --> SimpleTimePeriod (DG);

 * 13-Mar-2003 : Added equals(...) method, and Serializable interface (DG);

 * 21-Oct-2003 : Added hashCode() method (DG);

 *

 */



package org.jfree.data.time;



import java.io.Serializable;

import java.util.Date;



/**

 * An arbitrary period of time, measured to millisecond precision using <code>java.util.Date</code>.

 * <p>

 * This class is intentionally immutable (that is, once constructed, you cannot alter

 * the start and end attributes).

 */

public class SimpleTimePeriod implements TimePeriod, Serializable {



    /** The start date/time. */

    private Date start;



    /** The end date/time. */

    private Date end;



    /**

     * Creates a new time allocation.

     *

     * @param start  the start date/time (<code>null</code> not permitted).

     * @param end  the end date/time (<code>null</code> not permitted).

     */

    public SimpleTimePeriod(Date start, Date end) {

        if (start.getTime() > end.getTime()) {

            throw new IllegalArgumentException("SimpleTimePeriod: requires end >= start.");

        }

        this.start = start;

        this.end = end;

    }



    /**

     * Returns the start date/time.

     *

     * @return The start date/time (never <code>null</code>).

     */

    public Date getStart() {

        return this.start;

    }



    /**

     * Returns the end date/time.

     *

     * @return The end date/time (never <code>null</code>).

     */

    public Date getEnd() {

        return this.end;

    }



    /**

     * Returns <code>true</code> if this time period is equal to another object, and

     * <code>false</code> otherwise.

     * <P>

     * The test for equality looks only at the start and end values for the time period.

     *

     * @param obj  the other object (<code>null</code> permitted).

     *

     * @return A boolean.

     */

    public boolean equals(Object obj) {

        if (obj == this) {

            return true;

        }

        if (!(obj instanceof TimePeriod)) {

            return false;

        }

        TimePeriod that = (TimePeriod) obj;

        if (this.start.equals(that.getStart()) && (this.end.equals(that.getEnd()))) {

            return true;

        }

        return false;

    }

    

    /**

     * Returns a hash code for this object instance.

     * <p>

     * The approach described by Joshua Bloch in "Effective Java" has been used here:

     * <p>

     * <code>http://developer.java.sun.com/developer/Books/effectivejava/Chapter3.pdf</code>

     * 

     * @return A hash code.

     */

    public int hashCode() {

        int result = 17;

        result = 37 * result + this.start.hashCode();

        result = 37 * result + this.end.hashCode();

        return result;

    }



}

