1 /*
2 * Copyright (c) 2012, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 /*
27 * This file is available under and governed by the GNU General Public
28 * License version 2 only, as published by the Free Software Foundation.
29 * However, the following notice accompanied the original version of this
30 * file:
31 *
32 * Copyright (c) 2009-2012, Stephen Colebourne & Michael Nascimento Santos
33 *
34 * All rights reserved.
35 *
36 * Redistribution and use in source and binary forms, with or without
37 * modification, are permitted provided that the following conditions are met:
38 *
39 * * Redistributions of source code must retain the above copyright notice,
40 * this list of conditions and the following disclaimer.
41 *
42 * * Redistributions in binary form must reproduce the above copyright notice,
43 * this list of conditions and the following disclaimer in the documentation
44 * and/or other materials provided with the distribution.
45 *
46 * * Neither the name of JSR-310 nor the names of its contributors
47 * may be used to endorse or promote products derived from this software
48 * without specific prior written permission.
49 *
50 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
51 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
52 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
53 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
54 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
55 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
56 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
57 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
58 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
59 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
60 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
61 */
62 package java.time.zone;
63
64 import java.io.DataInput;
65 import java.io.DataOutput;
66 import java.io.IOException;
67 import java.io.InvalidObjectException;
68 import java.io.ObjectInputStream;
69 import java.io.Serializable;
70 import java.time.Duration;
71 import java.time.Instant;
72 import java.time.LocalDateTime;
73 import java.time.ZoneOffset;
74 import java.util.Arrays;
75 import java.util.Collections;
76 import java.util.List;
77 import java.util.Objects;
78
79 /**
80 * A transition between two offsets caused by a discontinuity in the local time-line.
81 * <p>
82 * A transition between two offsets is normally the result of a daylight savings cutover.
83 * The discontinuity is normally a gap in spring and an overlap in autumn.
84 * {@code ZoneOffsetTransition} models the transition between the two offsets.
85 * <p>
86 * Gaps occur where there are local date-times that simply do not exist.
87 * An example would be when the offset changes from {@code +03:00} to {@code +04:00}.
88 * This might be described as 'the clocks will move forward one hour tonight at 1am'.
89 * <p>
90 * Overlaps occur where there are local date-times that exist twice.
91 * An example would be when the offset changes from {@code +04:00} to {@code +03:00}.
92 * This might be described as 'the clocks will move back one hour tonight at 2am'.
93 *
94 * @implSpec
95 * This class is immutable and thread-safe.
96 *
97 * @since 1.8
98 */
99 public final class ZoneOffsetTransition
100 implements Comparable<ZoneOffsetTransition>, Serializable {
101
102 /**
103 * Serialization version.
104 */
105 private static final long serialVersionUID = -6946044323557704546L;
106 /**
107 * The transition epoch-second.
108 */
109 private final long epochSecond;
110 /**
111 * The local transition date-time at the transition.
112 */
113 private final LocalDateTime transition;
114 /**
115 * The offset before transition.
116 */
117 private final ZoneOffset offsetBefore;
118 /**
119 * The offset after transition.
120 */
121 private final ZoneOffset offsetAfter;
122
123 //-----------------------------------------------------------------------
124 /**
125 * Obtains an instance defining a transition between two offsets.
126 * <p>
127 * Applications should normally obtain an instance from {@link ZoneRules}.
128 * This factory is only intended for use when creating {@link ZoneRules}.
129 *
130 * @param transition the transition date-time at the transition, which never
131 * actually occurs, expressed local to the before offset, not null
132 * @param offsetBefore the offset before the transition, not null
133 * @param offsetAfter the offset at and after the transition, not null
134 * @return the transition, not null
135 * @throws IllegalArgumentException if {@code offsetBefore} and {@code offsetAfter}
136 * are equal, or {@code transition.getNano()} returns non-zero value
137 */
138 public static ZoneOffsetTransition of(LocalDateTime transition, ZoneOffset offsetBefore, ZoneOffset offsetAfter) {
139 Objects.requireNonNull(transition, "transition");
140 Objects.requireNonNull(offsetBefore, "offsetBefore");
141 Objects.requireNonNull(offsetAfter, "offsetAfter");
142 if (offsetBefore.equals(offsetAfter)) {
143 throw new IllegalArgumentException("Offsets must not be equal");
144 }
145 if (transition.getNano() != 0) {
146 throw new IllegalArgumentException("Nano-of-second must be zero");
147 }
148 return new ZoneOffsetTransition(transition, offsetBefore, offsetAfter);
149 }
150
151 /**
152 * Creates an instance defining a transition between two offsets.
153 *
154 * @param transition the transition date-time with the offset before the transition, not null
155 * @param offsetBefore the offset before the transition, not null
156 * @param offsetAfter the offset at and after the transition, not null
157 */
158 ZoneOffsetTransition(LocalDateTime transition, ZoneOffset offsetBefore, ZoneOffset offsetAfter) {
159 assert transition.getNano() == 0;
160 this.epochSecond = transition.toEpochSecond(offsetBefore);
161 this.transition = transition;
162 this.offsetBefore = offsetBefore;
163 this.offsetAfter = offsetAfter;
164 }
165
166 /**
167 * Creates an instance from epoch-second and offsets.
168 *
169 * @param epochSecond the transition epoch-second
170 * @param offsetBefore the offset before the transition, not null
171 * @param offsetAfter the offset at and after the transition, not null
172 */
173 ZoneOffsetTransition(long epochSecond, ZoneOffset offsetBefore, ZoneOffset offsetAfter) {
174 this.epochSecond = epochSecond;
175 this.transition = LocalDateTime.ofEpochSecond(epochSecond, 0, offsetBefore);
176 this.offsetBefore = offsetBefore;
177 this.offsetAfter = offsetAfter;
178 }
179
180 //-----------------------------------------------------------------------
181 /**
182 * Defend against malicious streams.
183 *
184 * @param s the stream to read
185 * @throws InvalidObjectException always
186 */
187 private void readObject(ObjectInputStream s) throws InvalidObjectException {
188 throw new InvalidObjectException("Deserialization via serialization delegate");
189 }
190
191 /**
192 * Writes the object using a
193 * <a href="../../../serialized-form.html#java.time.zone.Ser">dedicated serialized form</a>.
194 * @serialData
195 * Refer to the serialized form of
196 * <a href="../../../serialized-form.html#java.time.zone.ZoneRules">ZoneRules.writeReplace</a>
197 * for the encoding of epoch seconds and offsets.
198 * <pre style="font-size:1.0em">{@code
199 *
200 * out.writeByte(2); // identifies a ZoneOffsetTransition
201 * out.writeEpochSec(toEpochSecond);
202 * out.writeOffset(offsetBefore);
203 * out.writeOffset(offsetAfter);
204 * }
205 * </pre>
206 * @return the replacing object, not null
207 */
208 private Object writeReplace() {
209 return new Ser(Ser.ZOT, this);
210 }
211
212 /**
213 * Writes the state to the stream.
214 *
215 * @param out the output stream, not null
216 * @throws IOException if an error occurs
217 */
218 void writeExternal(DataOutput out) throws IOException {
219 Ser.writeEpochSec(epochSecond, out);
220 Ser.writeOffset(offsetBefore, out);
221 Ser.writeOffset(offsetAfter, out);
222 }
223
224 /**
225 * Reads the state from the stream.
226 *
227 * @param in the input stream, not null
228 * @return the created object, not null
229 * @throws IOException if an error occurs
230 */
231 static ZoneOffsetTransition readExternal(DataInput in) throws IOException {
232 long epochSecond = Ser.readEpochSec(in);
233 ZoneOffset before = Ser.readOffset(in);
234 ZoneOffset after = Ser.readOffset(in);
235 if (before.equals(after)) {
236 throw new IllegalArgumentException("Offsets must not be equal");
237 }
238 return new ZoneOffsetTransition(epochSecond, before, after);
239 }
240
241 //-----------------------------------------------------------------------
242 /**
243 * Gets the transition instant.
244 * <p>
245 * This is the instant of the discontinuity, which is defined as the first
246 * instant that the 'after' offset applies.
247 * <p>
248 * The methods {@link #getInstant()}, {@link #getDateTimeBefore()} and {@link #getDateTimeAfter()}
249 * all represent the same instant.
250 *
251 * @return the transition instant, not null
252 */
253 public Instant getInstant() {
254 return Instant.ofEpochSecond(epochSecond);
255 }
256
257 /**
258 * Gets the transition instant as an epoch second.
259 *
260 * @return the transition epoch second
261 */
262 public long toEpochSecond() {
263 return epochSecond;
264 }
265
266 //-------------------------------------------------------------------------
267 /**
268 * Gets the local transition date-time, as would be expressed with the 'before' offset.
269 * <p>
270 * This is the date-time where the discontinuity begins expressed with the 'before' offset.
271 * At this instant, the 'after' offset is actually used, therefore the combination of this
272 * date-time and the 'before' offset will never occur.
273 * <p>
274 * The combination of the 'before' date-time and offset represents the same instant
275 * as the 'after' date-time and offset.
276 *
277 * @return the transition date-time expressed with the before offset, not null
278 */
279 public LocalDateTime getDateTimeBefore() {
280 return transition;
281 }
282
283 /**
284 * Gets the local transition date-time, as would be expressed with the 'after' offset.
285 * <p>
286 * This is the first date-time after the discontinuity, when the new offset applies.
287 * <p>
288 * The combination of the 'before' date-time and offset represents the same instant
289 * as the 'after' date-time and offset.
290 *
291 * @return the transition date-time expressed with the after offset, not null
292 */
293 public LocalDateTime getDateTimeAfter() {
294 return transition.plusSeconds(getDurationSeconds());
295 }
296
297 /**
298 * Gets the offset before the transition.
299 * <p>
300 * This is the offset in use before the instant of the transition.
301 *
302 * @return the offset before the transition, not null
303 */
304 public ZoneOffset getOffsetBefore() {
305 return offsetBefore;
306 }
307
308 /**
309 * Gets the offset after the transition.
310 * <p>
311 * This is the offset in use on and after the instant of the transition.
312 *
313 * @return the offset after the transition, not null
314 */
315 public ZoneOffset getOffsetAfter() {
316 return offsetAfter;
317 }
318
319 /**
320 * Gets the duration of the transition.
321 * <p>
322 * In most cases, the transition duration is one hour, however this is not always the case.
323 * The duration will be positive for a gap and negative for an overlap.
324 * Time-zones are second-based, so the nanosecond part of the duration will be zero.
325 *
326 * @return the duration of the transition, positive for gaps, negative for overlaps
327 */
328 public Duration getDuration() {
329 return Duration.ofSeconds(getDurationSeconds());
330 }
331
332 /**
333 * Gets the duration of the transition in seconds.
334 *
335 * @return the duration in seconds
336 */
337 private int getDurationSeconds() {
338 return getOffsetAfter().getTotalSeconds() - getOffsetBefore().getTotalSeconds();
339 }
340
341 /**
342 * Does this transition represent a gap in the local time-line.
343 * <p>
344 * Gaps occur where there are local date-times that simply do not exist.
345 * An example would be when the offset changes from {@code +01:00} to {@code +02:00}.
346 * This might be described as 'the clocks will move forward one hour tonight at 1am'.
347 *
348 * @return true if this transition is a gap, false if it is an overlap
349 */
350 public boolean isGap() {
351 return getOffsetAfter().getTotalSeconds() > getOffsetBefore().getTotalSeconds();
352 }
353
354 /**
355 * Does this transition represent an overlap in the local time-line.
356 * <p>
357 * Overlaps occur where there are local date-times that exist twice.
358 * An example would be when the offset changes from {@code +02:00} to {@code +01:00}.
359 * This might be described as 'the clocks will move back one hour tonight at 2am'.
360 *
361 * @return true if this transition is an overlap, false if it is a gap
362 */
363 public boolean isOverlap() {
364 return getOffsetAfter().getTotalSeconds() < getOffsetBefore().getTotalSeconds();
365 }
366
367 /**
368 * Checks if the specified offset is valid during this transition.
369 * <p>
370 * This checks to see if the given offset will be valid at some point in the transition.
371 * A gap will always return false.
372 * An overlap will return true if the offset is either the before or after offset.
373 *
374 * @param offset the offset to check, null returns false
375 * @return true if the offset is valid during the transition
376 */
377 public boolean isValidOffset(ZoneOffset offset) {
378 return isGap() ? false : (getOffsetBefore().equals(offset) || getOffsetAfter().equals(offset));
379 }
380
381 /**
382 * Gets the valid offsets during this transition.
383 * <p>
384 * A gap will return an empty list, while an overlap will return both offsets.
385 *
386 * @return the list of valid offsets
387 */
388 List<ZoneOffset> getValidOffsets() {
389 if (isGap()) {
390 return List.of();
391 }
392 return List.of(getOffsetBefore(), getOffsetAfter());
393 }
394
395 //-----------------------------------------------------------------------
396 /**
397 * Compares this transition to another based on the transition instant.
398 * <p>
399 * This compares the instants of each transition.
400 * The offsets are ignored, making this order inconsistent with equals.
401 *
402 * @param transition the transition to compare to, not null
403 * @return the comparator value, negative if less, positive if greater
404 */
405 @Override
406 public int compareTo(ZoneOffsetTransition transition) {
407 return Long.compare(epochSecond, transition.epochSecond);
408 }
409
410 //-----------------------------------------------------------------------
411 /**
412 * Checks if this object equals another.
413 * <p>
414 * The entire state of the object is compared.
415 *
416 * @param other the other object to compare to, null returns false
417 * @return true if equal
418 */
419 @Override
420 public boolean equals(Object other) {
421 if (other == this) {
422 return true;
423 }
424 if (other instanceof ZoneOffsetTransition) {
425 ZoneOffsetTransition d = (ZoneOffsetTransition) other;
426 return epochSecond == d.epochSecond &&
427 offsetBefore.equals(d.offsetBefore) && offsetAfter.equals(d.offsetAfter);
428 }
429 return false;
430 }
431
432 /**
433 * Returns a suitable hash code.
434 *
435 * @return the hash code
436 */
437 @Override
438 public int hashCode() {
439 return transition.hashCode() ^ offsetBefore.hashCode() ^ Integer.rotateLeft(offsetAfter.hashCode(), 16);
440 }
441
442 //-----------------------------------------------------------------------
443 /**
444 * Returns a string describing this object.
445 *
446 * @return a string for debugging, not null
447 */
448 @Override
449 public String toString() {
450 StringBuilder buf = new StringBuilder();
451 buf.append("Transition[")
452 .append(isGap() ? "Gap" : "Overlap")
453 .append(" at ")
454 .append(transition)
455 .append(offsetBefore)
456 .append(" to ")
457 .append(offsetAfter)
458 .append(']');
459 return buf.toString();
460 }
461
462 }
463