001    /* ===========================================================
002     * JFreeChart : a free chart library for the Java(tm) platform
003     * ===========================================================
004     *
005     * (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.
006     *
007     * Project Info:  http://www.jfree.org/jfreechart/index.html
008     *
009     * This library is free software; you can redistribute it and/or modify it 
010     * under the terms of the GNU Lesser General Public License as published by 
011     * the Free Software Foundation; either version 2.1 of the License, or 
012     * (at your option) any later version.
013     *
014     * This library is distributed in the hope that it will be useful, but 
015     * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
016     * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
017     * License for more details.
018     *
019     * You should have received a copy of the GNU Lesser General Public
020     * License along with this library; if not, write to the Free Software
021     * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
022     * USA.  
023     *
024     * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
025     * in the United States and other countries.]
026     *
027     * ---------------------
028     * SimpleTimePeriod.java
029     * ---------------------
030     * (C) Copyright 2002-2005, by Object Refinery Limited and Contributors.
031     *
032     * Original Author:  David Gilbert (for Object Refinery Limited);
033     * Contributor(s):   -;
034     *
035     * $Id: SimpleTimePeriod.java,v 1.5.2.1 2005/10/25 21:35:24 mungady Exp $
036     *
037     * Changes
038     * -------
039     * 07-Oct-2002 : Added Javadocs (DG);
040     * 10-Jan-2003 : Renamed TimeAllocation --> SimpleTimePeriod (DG);
041     * 13-Mar-2003 : Added equals() method, and Serializable interface (DG);
042     * 21-Oct-2003 : Added hashCode() method (DG);
043     * 27-Jan-2005 : Implemented Comparable, to enable this class to be used
044     *               in the TimeTableXYDataset class (DG);
045     *
046     */
047    
048    package org.jfree.data.time;
049    
050    import java.io.Serializable;
051    import java.util.Date;
052    
053    /**
054     * An arbitrary period of time, measured to millisecond precision using 
055     * <code>java.util.Date</code>.
056     * <p>
057     * This class is intentionally immutable (that is, once constructed, you cannot 
058     * alter the start and end attributes).
059     */
060    public class SimpleTimePeriod implements TimePeriod, Comparable, Serializable {
061    
062        /** For serialization. */
063        private static final long serialVersionUID = 8684672361131829554L;
064        
065        /** The start date/time. */
066        private Date start;
067    
068        /** The end date/time. */
069        private Date end;
070    
071        /**
072         * Creates a new time allocation.
073         *
074         * @param start  the start date/time in milliseconds.
075         * @param end  the end date/time in milliseconds.
076         */
077        public SimpleTimePeriod(long start, long end) {
078            this(new Date(start), new Date(end));   
079        }
080        
081        /**
082         * Creates a new time allocation.
083         *
084         * @param start  the start date/time (<code>null</code> not permitted).
085         * @param end  the end date/time (<code>null</code> not permitted).
086         */
087        public SimpleTimePeriod(Date start, Date end) {
088            if (start.getTime() > end.getTime()) {
089                throw new IllegalArgumentException("Requires end >= start.");
090            }
091            this.start = start;
092            this.end = end;
093        }
094    
095        /**
096         * Returns the start date/time.
097         *
098         * @return The start date/time (never <code>null</code>).
099         */
100        public Date getStart() {
101            return this.start;
102        }
103    
104        /**
105         * Returns the end date/time.
106         *
107         * @return The end date/time (never <code>null</code>).
108         */
109        public Date getEnd() {
110            return this.end;
111        }
112    
113        /**
114         * Tests this time period instance for equality with an arbitrary object.  
115         * The object is considered equal if it is an instance of {@link TimePeriod}
116         * and it has the same start and end dates.
117         *
118         * @param obj  the other object (<code>null</code> permitted).
119         *
120         * @return A boolean.
121         */
122        public boolean equals(Object obj) {
123            if (obj == this) {
124                return true;
125            }
126            if (!(obj instanceof TimePeriod)) {
127                return false;
128            }
129            TimePeriod that = (TimePeriod) obj;
130            if (!this.start.equals(that.getStart())) {
131                return false;   
132            }
133            if (!this.end.equals(that.getEnd())) {
134                return false;   
135            }
136            return true;
137        }
138        
139        /**
140         * Returns an integer that indicates the relative ordering of two
141         * time periods.
142         * 
143         * @param obj  the object (<code>null</code> not permitted).
144         * 
145         * @return An integer.
146         * 
147         * @throws ClassCastException if <code>obj</code> is not an instance of
148         *                            {@link TimePeriod}.
149         */
150        public int compareTo(Object obj) {        
151            TimePeriod that = (TimePeriod) obj;
152            long t0 = getStart().getTime();
153            long t1 = getEnd().getTime();
154            long m0 = t0 + (t1 - t0) / 2L;
155            long t2 = that.getStart().getTime();
156            long t3 = that.getEnd().getTime();
157            long m1 = t2 + (t3 - t2) / 2L;
158            if (m0 < m1) {
159                return -1;   
160            }
161            else if (m0 > m1) {
162                return 1;   
163            }
164            else {
165                if (t0 < t2) {
166                    return -1;
167                }
168                else if (t0 > t2) {
169                    return 1;   
170                }
171                else {
172                    if (t1 < t3) {
173                        return -1;   
174                    }
175                    else if (t1 > t3) {
176                        return 1;   
177                    }
178                    else {
179                        return 0;   
180                    }
181                }
182            }
183        }
184        
185        /**
186         * Returns a hash code for this object instance.  The approach described by
187         * Joshua Bloch in "Effective Java" has been used here - see:
188         * <p>
189         * <code>http://developer.java.sun.com/
190         * developer/Books/effectivejava/Chapter3.pdf</code>
191         * 
192         * @return A hash code.
193         */
194        public int hashCode() {
195            int result = 17;
196            result = 37 * result + this.start.hashCode();
197            result = 37 * result + this.end.hashCode();
198            return result;
199        }
200    
201    }