001    /* ===========================================================
002     * JFreeChart : a free chart library for the Java(tm) platform
003     * ===========================================================
004     *
005     * (C) Copyright 2000-2007, 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 2002-2007, by Object Refinery Limited and Contributors.
031     *
032     * Original Author:  David Gilbert (for Object Refinery Limited);
033     * Contributor(s):   -;
034     *
035     * Changes
036     * -------
037     * 07-Oct-2002 : Added Javadocs (DG);
038     * 10-Jan-2003 : Renamed TimeAllocation --> SimpleTimePeriod (DG);
039     * 13-Mar-2003 : Added equals() method, and Serializable interface (DG);
040     * 21-Oct-2003 : Added hashCode() method (DG);
041     * 27-Jan-2005 : Implemented Comparable, to enable this class to be used
042     *               in the TimeTableXYDataset class (DG);
043     *
044     */
045    
046    package org.jfree.data.time;
047    
048    import java.io.Serializable;
049    import java.util.Date;
050    
051    /**
052     * An arbitrary period of time, measured to millisecond precision using 
053     * <code>java.util.Date</code>.
054     * <p>
055     * This class is intentionally immutable (that is, once constructed, you cannot 
056     * alter the start and end attributes).
057     */
058    public class SimpleTimePeriod implements TimePeriod, Comparable, Serializable {
059    
060        /** For serialization. */
061        private static final long serialVersionUID = 8684672361131829554L;
062        
063        /** The start date/time. */
064        private Date start;
065    
066        /** The end date/time. */
067        private Date end;
068    
069        /**
070         * Creates a new time allocation.
071         *
072         * @param start  the start date/time in milliseconds.
073         * @param end  the end date/time in milliseconds.
074         */
075        public SimpleTimePeriod(long start, long end) {
076            this(new Date(start), new Date(end));   
077        }
078        
079        /**
080         * Creates a new time allocation.
081         *
082         * @param start  the start date/time (<code>null</code> not permitted).
083         * @param end  the end date/time (<code>null</code> not permitted).
084         */
085        public SimpleTimePeriod(Date start, Date end) {
086            if (start.getTime() > end.getTime()) {
087                throw new IllegalArgumentException("Requires end >= start.");
088            }
089            this.start = start;
090            this.end = end;
091        }
092    
093        /**
094         * Returns the start date/time.
095         *
096         * @return The start date/time (never <code>null</code>).
097         */
098        public Date getStart() {
099            return this.start;
100        }
101    
102        /**
103         * Returns the end date/time.
104         *
105         * @return The end date/time (never <code>null</code>).
106         */
107        public Date getEnd() {
108            return this.end;
109        }
110    
111        /**
112         * Tests this time period instance for equality with an arbitrary object.  
113         * The object is considered equal if it is an instance of {@link TimePeriod}
114         * and it has the same start and end dates.
115         *
116         * @param obj  the other object (<code>null</code> permitted).
117         *
118         * @return A boolean.
119         */
120        public boolean equals(Object obj) {
121            if (obj == this) {
122                return true;
123            }
124            if (!(obj instanceof TimePeriod)) {
125                return false;
126            }
127            TimePeriod that = (TimePeriod) obj;
128            if (!this.start.equals(that.getStart())) {
129                return false;   
130            }
131            if (!this.end.equals(that.getEnd())) {
132                return false;   
133            }
134            return true;
135        }
136        
137        /**
138         * Returns an integer that indicates the relative ordering of two
139         * time periods.
140         * 
141         * @param obj  the object (<code>null</code> not permitted).
142         * 
143         * @return An integer.
144         * 
145         * @throws ClassCastException if <code>obj</code> is not an instance of
146         *                            {@link TimePeriod}.
147         */
148        public int compareTo(Object obj) {        
149            TimePeriod that = (TimePeriod) obj;
150            long t0 = getStart().getTime();
151            long t1 = getEnd().getTime();
152            long m0 = t0 + (t1 - t0) / 2L;
153            long t2 = that.getStart().getTime();
154            long t3 = that.getEnd().getTime();
155            long m1 = t2 + (t3 - t2) / 2L;
156            if (m0 < m1) {
157                return -1;   
158            }
159            else if (m0 > m1) {
160                return 1;   
161            }
162            else {
163                if (t0 < t2) {
164                    return -1;
165                }
166                else if (t0 > t2) {
167                    return 1;   
168                }
169                else {
170                    if (t1 < t3) {
171                        return -1;   
172                    }
173                    else if (t1 > t3) {
174                        return 1;   
175                    }
176                    else {
177                        return 0;   
178                    }
179                }
180            }
181        }
182        
183        /**
184         * Returns a hash code for this object instance.  The approach described by
185         * Joshua Bloch in "Effective Java" has been used here - see:
186         * <p>
187         * <code>http://developer.java.sun.com/
188         * developer/Books/effectivejava/Chapter3.pdf</code>
189         * 
190         * @return A hash code.
191         */
192        public int hashCode() {
193            int result = 17;
194            result = 37 * result + this.start.hashCode();
195            result = 37 * result + this.end.hashCode();
196            return result;
197        }
198    
199    }