001 /*
002 * Copyright 2001-2011 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 */
016 package org.joda.time;
017
018 /**
019 * Defines a partial time that does not support every datetime field, and is
020 * thus a local time.
021 * <p>
022 * A {@code ReadablePartial} supports a subset of those fields on the chronology.
023 * It cannot be compared to a {@code ReadableInstant}, as it does not fully
024 * specify an instant in time. The time it does specify is a local time, and does
025 * not include a time zone.
026 * <p>
027 * A {@code ReadablePartial} can be converted to a {@code ReadableInstant}
028 * using the {@code toDateTime} method. This works by providing a full base
029 * instant that can be used to 'fill in the gaps' and specify a time zone.
030 * <p>
031 * {@code ReadablePartial} is {@code Comparable} from v2.0.
032 * The comparison is based on the fields, compared in order, from largest to smallest.
033 * The first field that is non-equal is used to determine the result.
034 *
035 * @author Stephen Colebourne
036 * @since 1.0
037 */
038 public interface ReadablePartial extends Comparable<ReadablePartial> {
039
040 /**
041 * Gets the number of fields that this partial supports.
042 *
043 * @return the number of fields supported
044 */
045 int size();
046
047 /**
048 * Gets the field type at the specified index.
049 *
050 * @param index the index to retrieve
051 * @return the field at the specified index
052 * @throws IndexOutOfBoundsException if the index is invalid
053 */
054 DateTimeFieldType getFieldType(int index);
055
056 /**
057 * Gets the field at the specified index.
058 *
059 * @param index the index to retrieve
060 * @return the field at the specified index
061 * @throws IndexOutOfBoundsException if the index is invalid
062 */
063 DateTimeField getField(int index);
064
065 /**
066 * Gets the value at the specified index.
067 *
068 * @param index the index to retrieve
069 * @return the value of the field at the specified index
070 * @throws IndexOutOfBoundsException if the index is invalid
071 */
072 int getValue(int index);
073
074 /**
075 * Gets the chronology of the partial which is never null.
076 * <p>
077 * The {@link Chronology} is the calculation engine behind the partial and
078 * provides conversion and validation of the fields in a particular calendar system.
079 *
080 * @return the chronology, never null
081 */
082 Chronology getChronology();
083
084 /**
085 * Gets the value of one of the fields.
086 * <p>
087 * The field type specified must be one of those that is supported by the partial.
088 *
089 * @param field a DateTimeFieldType instance that is supported by this partial
090 * @return the value of that field
091 * @throws IllegalArgumentException if the field is null or not supported
092 */
093 int get(DateTimeFieldType field);
094
095 /**
096 * Checks whether the field type specified is supported by this partial.
097 *
098 * @param field the field to check, may be null which returns false
099 * @return true if the field is supported
100 */
101 boolean isSupported(DateTimeFieldType field);
102
103 /**
104 * Converts this partial to a full datetime by resolving it against another
105 * datetime.
106 * <p>
107 * This method takes the specified datetime and sets the fields from this
108 * instant on top. The chronology from the base instant is used.
109 * <p>
110 * For example, if this partial represents a time, then the result of this
111 * method will be the datetime from the specified base instant plus the
112 * time from this partial.
113 *
114 * @param baseInstant the instant that provides the missing fields, null means now
115 * @return the combined datetime
116 */
117 DateTime toDateTime(ReadableInstant baseInstant);
118
119 //-----------------------------------------------------------------------
120 /**
121 * Compares this partial with the specified object for equality based
122 * on the supported fields, chronology and values.
123 * <p>
124 * Two instances of ReadablePartial are equal if they have the same
125 * chronology, same field types (in same order) and same values.
126 *
127 * @param partial the object to compare to
128 * @return true if equal
129 */
130 boolean equals(Object partial);
131
132 /**
133 * Gets a hash code for the partial that is compatible with the
134 * equals method.
135 * <p>
136 * The formula used must be:
137 * <pre>
138 * int total = 157;
139 * for (int i = 0; i < fields.length; i++) {
140 * total = 23 * total + values[i];
141 * total = 23 * total + fieldTypes[i].hashCode();
142 * }
143 * total += chronology.hashCode();
144 * return total;
145 * </pre>
146 *
147 * @return a suitable hash code
148 */
149 int hashCode();
150
151 //-----------------------------------------------------------------------
152 // This is commented out to improve backwards compatibility
153 // /**
154 // * Compares this partial with another returning an integer
155 // * indicating the order.
156 // * <p>
157 // * The fields are compared in order, from largest to smallest.
158 // * The first field that is non-equal is used to determine the result.
159 // * Thus a year-hour partial will first be compared on the year, and then
160 // * on the hour.
161 // * <p>
162 // * The specified object must be a partial instance whose field types
163 // * match those of this partial. If the partial instance has different
164 // * fields then a {@code ClassCastException} is thrown.
165 // *
166 // * @param partial an object to check against
167 // * @return negative if this is less, zero if equal, positive if greater
168 // * @throws ClassCastException if the partial is the wrong class
169 // * or if it has field types that don't match
170 // * @throws NullPointerException if the partial is null
171 // * @since 2.0, previously on {@code AbstractPartial}
172 // */
173 // int compareTo(ReadablePartial partial);
174
175 //-----------------------------------------------------------------------
176 /**
177 * Get the value as a String in a recognisable ISO8601 format, only
178 * displaying supported fields.
179 * <p>
180 * The string output is in ISO8601 format to enable the String
181 * constructor to correctly parse it.
182 *
183 * @return the value as an ISO8601 string
184 */
185 String toString();
186
187 }