001/*
002 *  Copyright 2001-2005 Stephen Colebourne
003 *
004 *  Licensed under the Apache License, Version 2.0 (the "License");
005 *  you may not use this file except in compliance with the License.
006 *  You may obtain a copy of the License at
007 *
008 *      http://www.apache.org/licenses/LICENSE-2.0
009 *
010 *  Unless required by applicable law or agreed to in writing, software
011 *  distributed under the License is distributed on an "AS IS" BASIS,
012 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 *  See the License for the specific language governing permissions and
014 *  limitations under the License.
015 */
016package org.joda.time;
017
018/**
019 * Defines an exact duration of time in milliseconds.
020 * <p>
021 * The implementation of this interface may be mutable or immutable. This
022 * interface only gives access to retrieve data, never to change it.
023 * <p>
024 * Methods that are passed a duration as a parameter will treat <code>null</code>
025 * as a zero length duration.
026 *
027 * @see ReadableInterval
028 * @see ReadablePeriod
029 * @author Brian S O'Neill
030 * @author Stephen Colebourne
031 * @since 1.0
032 */
033public interface ReadableDuration extends Comparable {
034
035    /**
036     * Gets the total length of this duration in milliseconds.
037     *
038     * @return the total length of the time duration in milliseconds.
039     */
040    long getMillis();
041
042    //-----------------------------------------------------------------------
043    /**
044     * Get this duration as an immutable <code>Duration</code> object.
045     * <p>
046     * This will either typecast this instance, or create a new <code>Duration</code>.
047     * 
048     * @return a Duration created using the millisecond duration from this instance
049     */
050    Duration toDuration();
051
052    //-----------------------------------------------------------------------
053    /**
054     * Converts this duration to a Period instance using the standard period type
055     * and the ISO chronology.
056     * <p>
057     * Only precise fields in the period type will be used. Thus, only the hour,
058     * minute, second and millisecond fields on the period will be used.
059     * The year, month, week and day fields will not be populated.
060     * <p>
061     * If the duration is small, less than one day, then this method will perform
062     * as you might expect and split the fields evenly.
063     * If the duration is larger than one day then all the remaining duration will
064     * be stored in the largest available field, hours in this case.
065     * <p>
066     * For example, a duration effectively equal to (365 + 60 + 5) days will be
067     * converted to ((365 + 60 + 5) * 24) hours by this constructor.
068     * <p>
069     * For more control over the conversion process, you must pair the duration with
070     * an instant, see {@link Period#Period(ReadableInstant,ReadableDuration)}.
071     * 
072     * @return a Period created using the millisecond duration from this instance
073     */
074    Period toPeriod();
075
076    //-----------------------------------------------------------------------
077    /**
078     * Compares this duration with the specified duration based on length.
079     *
080     * @param obj  a duration to check against
081     * @return negative value if this is less, 0 if equal, or positive value if greater
082     * @throws NullPointerException if the object is null
083     * @throws ClassCastException if the given object is not supported
084     */
085    int compareTo(Object obj);
086
087    /**
088     * Is the length of this duration equal to the duration passed in.
089     *
090     * @param duration  another duration to compare to, null means zero milliseconds
091     * @return true if this duration is equal to than the duration passed in
092     */
093    boolean isEqual(ReadableDuration duration);
094
095    /**
096     * Is the length of this duration longer than the duration passed in.
097     *
098     * @param duration  another duration to compare to, null means zero milliseconds
099     * @return true if this duration is equal to than the duration passed in
100     */
101    boolean isLongerThan(ReadableDuration duration);
102
103    /**
104     * Is the length of this duration shorter than the duration passed in.
105     *
106     * @param duration  another duration to compare to, null means zero milliseconds
107     * @return true if this duration is equal to than the duration passed in
108     */
109    boolean isShorterThan(ReadableDuration duration);
110
111    //-----------------------------------------------------------------------
112    /**
113     * Compares this object with the specified object for equality based
114     * on the millisecond length. All ReadableDuration instances are accepted.
115     *
116     * @param readableDuration  a readable duration to check against
117     * @return true if the length of the duration is equal
118     */
119    boolean equals(Object readableDuration);
120
121    /**
122     * Gets a hash code for the duration that is compatable with the 
123     * equals method.
124     * The following formula must be used:
125     * <pre>
126     *  long len = getMillis();
127     *  return (int) (len ^ (len >>> 32));
128     * </pre>
129     *
130     * @return a hash code
131     */
132    int hashCode();
133
134    //-----------------------------------------------------------------------
135    /**
136     * Gets the value as a String in the ISO8601 duration format using hours,
137     * minutes and seconds (including fractional milliseconds).
138     * <p>
139     * For example, "PT6H3M7S" represents 6 hours, 3 minutes, 7 seconds.
140     *
141     * @return the value as an ISO8601 string
142     */
143    String toString();
144
145}