Java tutorial
/* * Copyright 2008 Google Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); you may not * use this file except in compliance with the License. You may obtain a copy of * the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations under * the License. */ package com.google.gwt.i18n.client; import com.google.gwt.core.client.JsArrayInteger; import com.google.gwt.core.client.JsArrayString; import java.util.Date; /** * The TimeZone class implements a time zone information source for client * applications. The time zone object is instantiated from a TimeZoneData object, * which is made from a JSON string that contains all the data needed for * the specified time zone. Applications can instantiate a time zone statically, * in which case the data could be retrieved from * the {@link com.google.gwt.i18n.client.constants.TimeZoneConstants TimeZoneConstants} * class. Applications can also choose to instantiate from a string obtained * from a server. The time zone string contains locale specific data. If the * application only uses a short representation, the English data will usually * satisfy the user's need. In the case that only the time zone offset is known, * there is a decent fallback that only uses the time zone offset to create a * TimeZone object. */ public class TimeZone implements com.google.gwt.i18n.shared.TimeZone { // constants to reference time zone names in the time zone names array private static final int STD_SHORT_NAME = 0; private static final int STD_LONG_NAME = 1; private static final int DLT_SHORT_NAME = 2; private static final int DLT_LONG_NAME = 3; /** * This factory method provides a decent fallback to create a time zone object * just based on a given time zone offset. * * @param timeZoneOffsetInMinutes time zone offset in minutes * @return a new time zone object */ public static TimeZone createTimeZone(int timeZoneOffsetInMinutes) { TimeZone tz = new TimeZone(); tz.standardOffset = timeZoneOffsetInMinutes; tz.timezoneID = composePOSIXTimeZoneID(timeZoneOffsetInMinutes); tz.tzNames = new String[2]; tz.tzNames[0] = composeUTCString(timeZoneOffsetInMinutes); tz.tzNames[1] = composeUTCString(timeZoneOffsetInMinutes); tz.transitionPoints = null; tz.adjustments = null; return tz; } /** * This factory method creates a time zone instance from a JSON string that * contains the time zone information for desired time zone. Applications can * get such a string from the TimeZoneConstants class, or it can request the * string from the server. Either way, the application obtains the original * string from the data provided in the TimeZoneConstant.properties file, * which was carefully prepared from CLDR and Olson time zone database. * * @param tzJSON JSON string that contains time zone data * @return a new time zone object */ public static TimeZone createTimeZone(String tzJSON) { TimeZoneInfo tzData = TimeZoneInfo.buildTimeZoneData(tzJSON); return createTimeZone(tzData); } public static TimeZone createTimeZone(TimeZoneInfo timezoneData) { TimeZone tz = new TimeZone(); tz.timezoneID = timezoneData.getID(); tz.standardOffset = -timezoneData.getStandardOffset(); JsArrayString jsTimezoneNames = timezoneData.getNames(); tz.tzNames = new String[jsTimezoneNames.length()]; for (int i = 0; i < jsTimezoneNames.length(); i++) { tz.tzNames[i] = jsTimezoneNames.get(i); } JsArrayInteger transitions = timezoneData.getTransitions(); if (transitions == null || transitions.length() == 0) { tz.transitionPoints = null; tz.adjustments = null; } else { int transitionNum = transitions.length() / 2; tz.transitionPoints = new int[transitionNum]; tz.adjustments = new int[transitionNum]; for (int i = 0; i < transitionNum; ++i) { tz.transitionPoints[i] = transitions.get(i * 2); tz.adjustments[i] = transitions.get(i * 2 + 1); } } return tz; } /** * In GMT representation, +/- has reverse sign of time zone offset. * when offset == 480, it should output GMT-08:00. */ private static String composeGMTString(int offset) { char data[] = { 'G', 'M', 'T', '-', '0', '0', ':', '0', '0' }; if (offset <= 0) { data[3] = '+'; offset = -offset; // suppress the '-' sign for text display. } data[4] += (offset / 60) / 10; data[5] += (offset / 60) % 10; data[7] += (offset % 60) / 10; data[8] += offset % 10; return new String(data); } /** * POSIX time zone ID as fallback. */ private static String composePOSIXTimeZoneID(int offset) { if (offset == 0) { return "Etc/GMT"; } String str; if (offset < 0) { offset = -offset; str = "Etc/GMT-"; } else { str = "Etc/GMT+"; } return str + offsetDisplay(offset); } private static String composeUTCString(int offset) { if (offset == 0) { return "UTC"; } String str; if (offset < 0) { offset = -offset; str = "UTC+"; } else { str = "UTC-"; } return str + offsetDisplay(offset); } private static String offsetDisplay(int offset) { int hour = offset / 60; int mins = offset % 60; if (mins == 0) { return Integer.toString(hour); } return Integer.toString(hour) + ":" + Integer.toString(mins); } private String timezoneID; private int standardOffset; private String[] tzNames; private int[] transitionPoints; private int[] adjustments; private TimeZone() { } /* (non-Javadoc) * @see com.google.gwt.i18n.client.TimeZoneIntf#getDaylightAdjustment(java.util.Date) */ public int getDaylightAdjustment(Date date) { if (transitionPoints == null) { return 0; } long timeInHours = date.getTime() / 1000 / 3600; int index = 0; while (index < transitionPoints.length && timeInHours >= transitionPoints[index]) { ++index; } return (index == 0) ? 0 : adjustments[index - 1]; } /* (non-Javadoc) * @see com.google.gwt.i18n.client.TimeZoneIntf#getGMTString(java.util.Date) */ public String getGMTString(Date date) { return composeGMTString(getOffset(date)); } /* (non-Javadoc) * @see com.google.gwt.i18n.client.TimeZoneIntf#getID() */ public String getID() { return timezoneID; } /* (non-Javadoc) * @see com.google.gwt.i18n.client.TimeZoneIntf#getISOTimeZoneString(java.util.Date) */ public String getISOTimeZoneString(Date date) { int offset = -getOffset(date); char data[] = { '+', '0', '0', ':', '0', '0' }; if (offset < 0) { data[0] = '-'; offset = -offset; // suppress the '-' sign for text display. } data[1] += (offset / 60) / 10; data[2] += (offset / 60) % 10; data[4] += (offset % 60) / 10; data[5] += offset % 10; return new String(data); } /* (non-Javadoc) * @see com.google.gwt.i18n.client.TimeZoneIntf#getLongName(java.util.Date) */ public String getLongName(Date date) { return tzNames[isDaylightTime(date) ? DLT_LONG_NAME : STD_LONG_NAME]; } /* (non-Javadoc) * @see com.google.gwt.i18n.client.TimeZoneIntf#getOffset(java.util.Date) */ public int getOffset(Date date) { return standardOffset - getDaylightAdjustment(date); } /* (non-Javadoc) * @see com.google.gwt.i18n.client.TimeZoneIntf#getRFCTimeZoneString(java.util.Date) */ public String getRFCTimeZoneString(Date date) { int offset = -getOffset(date); char data[] = { '+', '0', '0', '0', '0' }; if (offset < 0) { data[0] = '-'; offset = -offset; // suppress the '-' sign for text display. } data[1] += (offset / 60) / 10; data[2] += (offset / 60) % 10; data[3] += (offset % 60) / 10; data[4] += offset % 10; return new String(data); } /* (non-Javadoc) * @see com.google.gwt.i18n.client.TimeZoneIntf#getShortName(java.util.Date) */ public String getShortName(Date date) { return tzNames[isDaylightTime(date) ? DLT_SHORT_NAME : STD_SHORT_NAME]; } /* (non-Javadoc) * @see com.google.gwt.i18n.client.TimeZoneIntf#getStandardOffset() */ public int getStandardOffset() { return standardOffset; } /* (non-Javadoc) * @see com.google.gwt.i18n.client.TimeZoneIntf#isDaylightTime(java.util.Date) */ public boolean isDaylightTime(Date date) { return getDaylightAdjustment(date) > 0; } }