1 /*
2 * Copyright (c) 2012, 2013, 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 this.epochSecond = transition.toEpochSecond(offsetBefore);
160 this.transition = transition;
161 this.offsetBefore = offsetBefore;
162 this.offsetAfter = offsetAfter;
163 }
164
165 /**
166 * Creates an instance from epoch-second and offsets.
167 *
168 * @param epochSecond the transition epoch-second
169 * @param offsetBefore the offset before the transition, not null
170 * @param offsetAfter the offset at and after the transition, not null
171 */
172 ZoneOffsetTransition(long epochSecond, ZoneOffset offsetBefore, ZoneOffset offsetAfter) {
173 this.epochSecond = epochSecond;
174 this.transition = LocalDateTime.ofEpochSecond(epochSecond, 0, offsetBefore);
175 this.offsetBefore = offsetBefore;
176 this.offsetAfter = offsetAfter;
177 }
178
179 //-----------------------------------------------------------------------
180 /**
181 * Defend against malicious streams.
182 *
183 * @param s the stream to read
184 * @throws InvalidObjectException always
185 */
186 private void readObject(ObjectInputStream s) throws InvalidObjectException {
187 throw new InvalidObjectException("Deserialization via serialization delegate");
188 }
189
190 /**
191 * Writes the object using a
192 * <a href="../../../serialized-form.html#java.time.zone.Ser">dedicated serialized form</a>.
193 * @serialData
194 * Refer to the serialized form of
195 * <a href="../../../serialized-form.html#java.time.zone.ZoneRules">ZoneRules.writeReplace</a>
196 * for the encoding of epoch seconds and offsets.
197 * <pre style="font-size:1.0em">{@code
198 *
199 * out.writeByte(2); // identifies a ZoneOffsetTransition
200 * out.writeEpochSec(toEpochSecond);
201 * out.writeOffset(offsetBefore);
202 * out.writeOffset(offsetAfter);
203 * }
204 * </pre>
205 * @return the replacing object, not null
206 */
207 private Object writeReplace() {
208 return new Ser(Ser.ZOT, this);
209 }
210
211 /**
212 * Writes the state to the stream.
213 *
214 * @param out the output stream, not null
215 * @throws IOException if an error occurs
216 */
217 void writeExternal(DataOutput out) throws IOException {
218 Ser.writeEpochSec(epochSecond, out);
219 Ser.writeOffset(offsetBefore, out);
220 Ser.writeOffset(offsetAfter, out);
221 }
222
223 /**
224 * Reads the state from the stream.
225 *
226 * @param in the input stream, not null
227 * @return the created object, not null
228 * @throws IOException if an error occurs
229 */
230 static ZoneOffsetTransition readExternal(DataInput in) throws IOException {
231 long epochSecond = Ser.readEpochSec(in);
232 ZoneOffset before = Ser.readOffset(in);
233 ZoneOffset after = Ser.readOffset(in);
234 if (before.equals(after)) {
235 throw new IllegalArgumentException("Offsets must not be equal");
236 }
237 return new ZoneOffsetTransition(epochSecond, before, after);
238 }
239
240 //-----------------------------------------------------------------------
241 /**
242 * Gets the transition instant.
243 * <p>
244 * This is the instant of the discontinuity, which is defined as the first
245 * instant that the 'after' offset applies.
246 * <p>
247 * The methods {@link #getInstant()}, {@link #getDateTimeBefore()} and {@link #getDateTimeAfter()}
248 * all represent the same instant.
249 *
250 * @return the transition instant, not null
251 */
252 public Instant getInstant() {
253 return Instant.ofEpochSecond(epochSecond);
254 }
255
256 /**
257 * Gets the transition instant as an epoch second.
258 *
259 * @return the transition epoch second
260 */
261 public long toEpochSecond() {
262 return epochSecond;
263 }
264
265 //-------------------------------------------------------------------------
266 /**
267 * Gets the local transition date-time, as would be expressed with the 'before' offset.
268 * <p>
269 * This is the date-time where the discontinuity begins expressed with the 'before' offset.
270 * At this instant, the 'after' offset is actually used, therefore the combination of this
271 * date-time and the 'before' offset will never occur.
272 * <p>
273 * The combination of the 'before' date-time and offset represents the same instant
274 * as the 'after' date-time and offset.
275 *
276 * @return the transition date-time expressed with the before offset, not null
277 */
278 public LocalDateTime getDateTimeBefore() {
279 return transition;
280 }
281
282 /**
283 * Gets the local transition date-time, as would be expressed with the 'after' offset.
284 * <p>
285 * This is the first date-time after the discontinuity, when the new offset applies.
286 * <p>
287 * The combination of the 'before' date-time and offset represents the same instant
288 * as the 'after' date-time and offset.
289 *
290 * @return the transition date-time expressed with the after offset, not null
291 */
292 public LocalDateTime getDateTimeAfter() {
293 return transition.plusSeconds(getDurationSeconds());
294 }
295
296 /**
297 * Gets the offset before the transition.
298 * <p>
299 * This is the offset in use before the instant of the transition.
300 *
301 * @return the offset before the transition, not null
302 */
303 public ZoneOffset getOffsetBefore() {
304 return offsetBefore;
305 }
306
307 /**
308 * Gets the offset after the transition.
309 * <p>
310 * This is the offset in use on and after the instant of the transition.
311 *
312 * @return the offset after the transition, not null
313 */
314 public ZoneOffset getOffsetAfter() {
315 return offsetAfter;
316 }
317
318 /**
319 * Gets the duration of the transition.
320 * <p>
321 * In most cases, the transition duration is one hour, however this is not always the case.
322 * The duration will be positive for a gap and negative for an overlap.
323 * Time-zones are second-based, so the nanosecond part of the duration will be zero.
324 *
325 * @return the duration of the transition, positive for gaps, negative for overlaps
326 */
327 public Duration getDuration() {
328 return Duration.ofSeconds(getDurationSeconds());
329 }
330
331 /**
332 * Gets the duration of the transition in seconds.
333 *
334 * @return the duration in seconds
335 */
336 private int getDurationSeconds() {
337 return getOffsetAfter().getTotalSeconds() - getOffsetBefore().getTotalSeconds();
338 }
339
340 /**
341 * Does this transition represent a gap in the local time-line.
342 * <p>
343 * Gaps occur where there are local date-times that simply do not exist.
344 * An example would be when the offset changes from {@code +01:00} to {@code +02:00}.
345 * This might be described as 'the clocks will move forward one hour tonight at 1am'.
346 *
347 * @return true if this transition is a gap, false if it is an overlap
348 */
349 public boolean isGap() {
350 return getOffsetAfter().getTotalSeconds() > getOffsetBefore().getTotalSeconds();
351 }
352
353 /**
354 * Does this transition represent an overlap in the local time-line.
355 * <p>
356 * Overlaps occur where there are local date-times that exist twice.
357 * An example would be when the offset changes from {@code +02:00} to {@code +01:00}.
358 * This might be described as 'the clocks will move back one hour tonight at 2am'.
359 *
360 * @return true if this transition is an overlap, false if it is a gap
361 */
362 public boolean isOverlap() {
363 return getOffsetAfter().getTotalSeconds() < getOffsetBefore().getTotalSeconds();
364 }
365
366 /**
367 * Checks if the specified offset is valid during this transition.
368 * <p>
369 * This checks to see if the given offset will be valid at some point in the transition.
370 * A gap will always return false.
371 * An overlap will return true if the offset is either the before or after offset.
372 *
373 * @param offset the offset to check, null returns false
374 * @return true if the offset is valid during the transition
375 */
376 public boolean isValidOffset(ZoneOffset offset) {
377 return isGap() ? false : (getOffsetBefore().equals(offset) || getOffsetAfter().equals(offset));
378 }
379
380 /**
381 * Gets the valid offsets during this transition.
382 * <p>
383 * A gap will return an empty list, while an overlap will return both offsets.
384 *
385 * @return the list of valid offsets
386 */
387 List<ZoneOffset> getValidOffsets() {
388 if (isGap()) {
389 return Collections.emptyList();
390 }
391 return Arrays.asList(getOffsetBefore(), getOffsetAfter());
392 }
393
394 //-----------------------------------------------------------------------
395 /**
396 * Compares this transition to another based on the transition instant.
397 * <p>
398 * This compares the instants of each transition.
399 * The offsets are ignored, making this order inconsistent with equals.
400 *
401 * @param transition the transition to compare to, not null
402 * @return the comparator value, negative if less, positive if greater
403 */
404 @Override
405 public int compareTo(ZoneOffsetTransition transition) {
406 return Long.compare(epochSecond, transition.epochSecond);
407 }
408
409 //-----------------------------------------------------------------------
410 /**
411 * Checks if this object equals another.
412 * <p>
413 * The entire state of the object is compared.
414 *
415 * @param other the other object to compare to, null returns false
416 * @return true if equal
417 */
418 @Override
419 public boolean equals(Object other) {
420 if (other == this) {
421 return true;
422 }
423 if (other instanceof ZoneOffsetTransition) {
424 ZoneOffsetTransition d = (ZoneOffsetTransition) other;
425 return epochSecond == d.epochSecond &&
426 offsetBefore.equals(d.offsetBefore) && offsetAfter.equals(d.offsetAfter);
427 }
428 return false;
429 }
430
431 /**
432 * Returns a suitable hash code.
433 *
434 * @return the hash code
435 */
436 @Override
437 public int hashCode() {
438 return transition.hashCode() ^ offsetBefore.hashCode() ^ Integer.rotateLeft(offsetAfter.hashCode(), 16);
439 }
440
441 //-----------------------------------------------------------------------
442 /**
443 * Returns a string describing this object.
444 *
445 * @return a string for debugging, not null
446 */
447 @Override
448 public String toString() {
449 StringBuilder buf = new StringBuilder();
450 buf.append("Transition[")
451 .append(isGap() ? "Gap" : "Overlap")
452 .append(" at ")
453 .append(transition)
454 .append(offsetBefore)
455 .append(" to ")
456 .append(offsetAfter)
457 .append(']');
458 return buf.toString();
459 }
460
461 }