1/* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18package java.util; 19 20import java.io.IOException; 21import java.io.Serializable; 22import java.util.regex.Matcher; 23import java.util.regex.Pattern; 24import libcore.icu.TimeZones; 25import libcore.util.ZoneInfoDB; 26 27/** 28 * {@code TimeZone} represents a time zone, primarily used for configuring a {@link Calendar} or 29 * {@link java.text.SimpleDateFormat} instance. 30 * 31 * <p>Most applications will use {@link #getDefault} which returns a {@code TimeZone} based on 32 * the time zone where the program is running. 33 * 34 * <p>You can also get a specific {@code TimeZone} {@link #getTimeZone by Olson ID}. 35 * 36 * <p>It is highly unlikely you'll ever want to use anything but the factory methods yourself. 37 * Let classes like {@link Calendar} and {@link java.text.SimpleDateFormat} do the date 38 * computations for you. 39 * 40 * <p>If you do need to do date computations manually, there are two common cases to take into 41 * account: 42 * <ul> 43 * <li>Somewhere like California, where daylight time is used. 44 * The {@link #useDaylightTime} method will always return true, and {@link #inDaylightTime} 45 * must be used to determine whether or not daylight time applies to a given {@code Date}. 46 * The {@link #getRawOffset} method will return a raw offset of (in this case) -8 hours from UTC, 47 * which isn't usually very useful. More usefully, the {@link #getOffset} methods return the 48 * actual offset from UTC <i>for a given point in time</i>; this is the raw offset plus (if the 49 * point in time is {@link #inDaylightTime in daylight time}) the applicable 50 * {@link #getDSTSavings DST savings} (usually, but not necessarily, 1 hour). 51 * <li>Somewhere like Japan, where daylight time is not used. 52 * The {@link #useDaylightTime} and {@link #inDaylightTime} methods both always return false, 53 * and the raw and actual offsets will always be the same. 54 * </ul> 55 * 56 * <p>Note the type returned by the factory methods {@link #getDefault} and {@link #getTimeZone} is 57 * implementation dependent. This may introduce serialization incompatibility issues between 58 * different implementations. Android returns instances of {@link SimpleTimeZone} so that 59 * the bytes serialized by Android can be deserialized successfully on other 60 * implementations, but the reverse compatibility cannot be guaranteed. 61 * 62 * @see Calendar 63 * @see GregorianCalendar 64 * @see SimpleDateFormat 65 * @see SimpleTimeZone 66 */ 67public abstract class TimeZone implements Serializable, Cloneable { 68 private static final long serialVersionUID = 3581463369166924961L; 69 70 private static final Pattern CUSTOM_ZONE_ID_PATTERN = Pattern.compile("^GMT[-+](\\d{1,2})(:?(\\d\\d))?$"); 71 72 /** 73 * The short display name style, such as {@code PDT}. Requests for this 74 * style may yield GMT offsets like {@code GMT-08:00}. 75 */ 76 public static final int SHORT = 0; 77 78 /** 79 * The long display name style, such as {@code Pacific Daylight Time}. 80 * Requests for this style may yield GMT offsets like {@code GMT-08:00}. 81 */ 82 public static final int LONG = 1; 83 84 private static final TimeZone GMT = new SimpleTimeZone(0, "GMT"); 85 private static final TimeZone UTC = new SimpleTimeZone(0, "UTC"); 86 87 private static TimeZone defaultTimeZone; 88 89 private String ID; 90 91 public TimeZone() {} 92 93 /** 94 * Returns a new time zone with the same ID, raw offset, and daylight 95 * savings time rules as this time zone. 96 */ 97 @Override public Object clone() { 98 try { 99 return super.clone(); 100 } catch (CloneNotSupportedException e) { 101 throw new AssertionError(e); 102 } 103 } 104 105 /** 106 * Returns the system's installed time zone IDs. Any of these IDs can be 107 * passed to {@link #getTimeZone} to lookup the corresponding time zone 108 * instance. 109 */ 110 public static synchronized String[] getAvailableIDs() { 111 return ZoneInfoDB.getAvailableIDs(); 112 } 113 114 /** 115 * Returns the IDs of the time zones whose offset from UTC is {@code 116 * offsetMillis}. Any of these IDs can be passed to {@link #getTimeZone} to 117 * lookup the corresponding time zone instance. 118 * 119 * @return a possibly-empty array. 120 */ 121 public static synchronized String[] getAvailableIDs(int offsetMillis) { 122 return ZoneInfoDB.getAvailableIDs(offsetMillis); 123 } 124 125 /** 126 * Returns the user's preferred time zone. This may have been overridden for 127 * this process with {@link #setDefault}. 128 * 129 * <p>Since the user's time zone changes dynamically, avoid caching this 130 * value. Instead, use this method to look it up for each use. 131 */ 132 public static synchronized TimeZone getDefault() { 133 if (defaultTimeZone == null) { 134 defaultTimeZone = ZoneInfoDB.getSystemDefault(); 135 } 136 return (TimeZone) defaultTimeZone.clone(); 137 } 138 139 /** 140 * Equivalent to {@code getDisplayName(false, TimeZone.LONG, Locale.getDefault())}. 141 * <a href="../util/Locale.html#default_locale">Be wary of the default locale</a>. 142 */ 143 public final String getDisplayName() { 144 return getDisplayName(false, LONG, Locale.getDefault()); 145 } 146 147 /** 148 * Equivalent to {@code getDisplayName(false, TimeZone.LONG, locale)}. 149 */ 150 public final String getDisplayName(Locale locale) { 151 return getDisplayName(false, LONG, locale); 152 } 153 154 /** 155 * Equivalent to {@code getDisplayName(daylightTime, style, Locale.getDefault())}. 156 * <a href="../util/Locale.html#default_locale">Be wary of the default locale</a>. 157 */ 158 public final String getDisplayName(boolean daylightTime, int style) { 159 return getDisplayName(daylightTime, style, Locale.getDefault()); 160 } 161 162 /** 163 * Returns the {@link #SHORT short} or {@link #LONG long} name of this time 164 * zone with either standard or daylight time, as written in {@code locale}. 165 * If the name is not available, the result is in the format 166 * {@code GMT[+-]hh:mm}. 167 * 168 * @param daylightTime true for daylight time, false for standard time. 169 * @param style either {@link TimeZone#LONG} or {@link TimeZone#SHORT}. 170 * @param locale the display locale. 171 */ 172 public String getDisplayName(boolean daylightTime, int style, Locale locale) { 173 if (style != SHORT && style != LONG) { 174 throw new IllegalArgumentException(); 175 } 176 177 boolean useDaylight = daylightTime && useDaylightTime(); 178 179 String[][] zoneStrings = TimeZones.getZoneStrings(locale); 180 String result = TimeZones.getDisplayName(zoneStrings, getID(), daylightTime, style); 181 if (result != null) { 182 return result; 183 } 184 185 // TODO: do we ever get here? 186 187 int offset = getRawOffset(); 188 if (useDaylight && this instanceof SimpleTimeZone) { 189 offset += getDSTSavings(); 190 } 191 offset /= 60000; 192 char sign = '+'; 193 if (offset < 0) { 194 sign = '-'; 195 offset = -offset; 196 } 197 StringBuilder builder = new StringBuilder(9); 198 builder.append("GMT"); 199 builder.append(sign); 200 appendNumber(builder, 2, offset / 60); 201 builder.append(':'); 202 appendNumber(builder, 2, offset % 60); 203 return builder.toString(); 204 } 205 206 private void appendNumber(StringBuilder builder, int count, int value) { 207 String string = Integer.toString(value); 208 for (int i = 0; i < count - string.length(); i++) { 209 builder.append('0'); 210 } 211 builder.append(string); 212 } 213 214 /** 215 * Returns the ID of this {@code TimeZone}, such as 216 * {@code America/Los_Angeles}, {@code GMT-08:00} or {@code UTC}. 217 */ 218 public String getID() { 219 return ID; 220 } 221 222 /** 223 * Returns the latest daylight savings in milliseconds for this time zone, relative 224 * to this time zone's regular UTC offset (as returned by {@link #getRawOffset}). 225 * 226 * <p>This class returns {@code 3600000} (1 hour) for time zones 227 * that use daylight savings time and {@code 0} for timezones that do not, 228 * leaving it to subclasses to override this method for other daylight savings 229 * offsets. (There are time zones, such as {@code Australia/Lord_Howe}, 230 * that use other values.) 231 * 232 * <p>Note that this method doesn't tell you whether or not to <i>apply</i> the 233 * offset: you need to call {@code inDaylightTime} for the specific time 234 * you're interested in. If this method returns a non-zero offset, that only 235 * tells you that this {@code TimeZone} sometimes observes daylight savings. 236 * 237 * <p>Note also that this method doesn't necessarily return the value you need 238 * to apply to the time you're working with. This value can and does change over 239 * time for a given time zone. 240 * 241 * <p>It's highly unlikely that you should ever call this method. You 242 * probably want {@link #getOffset} instead, which tells you the offset 243 * for a specific point in time, and takes daylight savings into account for you. 244 */ 245 public int getDSTSavings() { 246 return useDaylightTime() ? 3600000 : 0; 247 } 248 249 /** 250 * Returns the offset in milliseconds from UTC for this time zone at {@code 251 * time}. The offset includes daylight savings time if the specified 252 * date is within the daylight savings time period. 253 * 254 * @param time the date in milliseconds since January 1, 1970 00:00:00 UTC 255 */ 256 public int getOffset(long time) { 257 if (inDaylightTime(new Date(time))) { 258 return getRawOffset() + getDSTSavings(); 259 } 260 return getRawOffset(); 261 } 262 263 /** 264 * Returns this time zone's offset in milliseconds from UTC at the specified 265 * date and time. The offset includes daylight savings time if the date 266 * and time is within the daylight savings time period. 267 * 268 * <p>This method is intended to be used by {@link Calendar} to compute 269 * {@link Calendar#DST_OFFSET} and {@link Calendar#ZONE_OFFSET}. Application 270 * code should have no reason to call this method directly. Each parameter 271 * is interpreted in the same way as the corresponding {@code Calendar} 272 * field. Refer to {@link Calendar} for specific definitions of this 273 * method's parameters. 274 */ 275 public abstract int getOffset(int era, int year, int month, int day, 276 int dayOfWeek, int timeOfDayMillis); 277 278 /** 279 * Returns the offset in milliseconds from UTC of this time zone's standard 280 * time. 281 */ 282 public abstract int getRawOffset(); 283 284 /** 285 * Returns a {@code TimeZone} corresponding to the given {@code id}, or {@code GMT} 286 * for unknown ids. 287 * 288 * <p>An ID can be an Olson name of the form <i>Area</i>/<i>Location</i>, such 289 * as {@code America/Los_Angeles}. The {@link #getAvailableIDs} method returns 290 * the supported names. 291 * 292 * <p>This method can also create a custom {@code TimeZone} given an ID with the following 293 * syntax: {@code GMT[+|-]hh[[:]mm]}. For example, {@code "GMT+05:00"}, {@code "GMT+0500"}, 294 * {@code "GMT+5:00"}, {@code "GMT+500"}, {@code "GMT+05"}, and {@code "GMT+5"} all return 295 * an object with a raw offset of +5 hours from UTC, and which does <i>not</i> use daylight 296 * savings. These are rarely useful, because they don't correspond to time zones actually 297 * in use by humans. 298 * 299 * <p>Other than the special cases "UTC" and "GMT" (which are synonymous in this context, 300 * both corresponding to UTC), Android does not support the deprecated three-letter time 301 * zone IDs used in Java 1.1. 302 */ 303 public static synchronized TimeZone getTimeZone(String id) { 304 if (id == null) { 305 throw new NullPointerException("id == null"); 306 } 307 308 // Special cases? These can clone an existing instance. 309 // TODO: should we just add a cache to ZoneInfoDB instead? 310 if (id.length() == 3) { 311 if (id.equals("GMT")) { 312 return (TimeZone) GMT.clone(); 313 } 314 if (id.equals("UTC")) { 315 return (TimeZone) UTC.clone(); 316 } 317 } 318 319 // In the database? 320 TimeZone zone = null; 321 try { 322 zone = ZoneInfoDB.makeTimeZone(id); 323 } catch (IOException ignored) { 324 } 325 326 // Custom time zone? 327 if (zone == null && id.length() > 3 && id.startsWith("GMT")) { 328 zone = getCustomTimeZone(id); 329 } 330 331 // We never return null; on failure we return the equivalent of "GMT". 332 return (zone != null) ? zone : (TimeZone) GMT.clone(); 333 } 334 335 /** 336 * Returns a new SimpleTimeZone for an ID of the form "GMT[+|-]hh[[:]mm]", or null. 337 */ 338 private static TimeZone getCustomTimeZone(String id) { 339 Matcher m = CUSTOM_ZONE_ID_PATTERN.matcher(id); 340 if (!m.matches()) { 341 return null; 342 } 343 344 int hour; 345 int minute = 0; 346 try { 347 hour = Integer.parseInt(m.group(1)); 348 if (m.group(3) != null) { 349 minute = Integer.parseInt(m.group(3)); 350 } 351 } catch (NumberFormatException impossible) { 352 throw new AssertionError(impossible); 353 } 354 355 if (hour < 0 || hour > 23 || minute < 0 || minute > 59) { 356 return null; 357 } 358 359 char sign = id.charAt(3); 360 int raw = (hour * 3600000) + (minute * 60000); 361 if (sign == '-') { 362 raw = -raw; 363 } 364 365 String cleanId = String.format("GMT%c%02d:%02d", sign, hour, minute); 366 return new SimpleTimeZone(raw, cleanId); 367 } 368 369 /** 370 * Returns true if {@code timeZone} has the same rules as this time zone. 371 * 372 * <p>The base implementation returns true if both time zones have the same 373 * raw offset. 374 */ 375 public boolean hasSameRules(TimeZone timeZone) { 376 if (timeZone == null) { 377 return false; 378 } 379 return getRawOffset() == timeZone.getRawOffset(); 380 } 381 382 /** 383 * Returns true if {@code time} is in a daylight savings time period for 384 * this time zone. 385 */ 386 public abstract boolean inDaylightTime(Date time); 387 388 /** 389 * Overrides the default time zone for the current process only. 390 * 391 * <p><strong>Warning</strong>: avoid using this method to use a custom time 392 * zone in your process. This value may be cleared or overwritten at any 393 * time, which can cause unexpected behavior. Instead, manually supply a 394 * custom time zone as needed. 395 * 396 * @param timeZone a custom time zone, or {@code null} to set the default to 397 * the user's preferred value. 398 */ 399 public static synchronized void setDefault(TimeZone timeZone) { 400 defaultTimeZone = timeZone != null ? (TimeZone) timeZone.clone() : null; 401 } 402 403 /** 404 * Sets the ID of this {@code TimeZone}. 405 */ 406 public void setID(String id) { 407 if (id == null) { 408 throw new NullPointerException("id == null"); 409 } 410 ID = id; 411 } 412 413 /** 414 * Sets the offset in milliseconds from UTC of this time zone's standard 415 * time. 416 */ 417 public abstract void setRawOffset(int offsetMillis); 418 419 /** 420 * Returns true if this time zone has a future transition to or from 421 * daylight savings time. 422 * 423 * <p><strong>Warning:</strong> this returns false for time zones like 424 * {@code Asia/Kuala_Lumpur} that have previously used DST but do not 425 * currently. A hypothetical country that has never observed daylight 426 * savings before but plans to start next year would return true. 427 * 428 * <p><strong>Warning:</strong> this returns true for time zones that use 429 * DST, even when it is not active. 430 * 431 * <p>Use {@link #inDaylightTime} to find out whether daylight savings is 432 * in effect at a specific time. 433 * 434 * <p>Most applications should not use this method. 435 */ 436 public abstract boolean useDaylightTime(); 437} 438