calendar.java

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    zone = TimeZone.getDefault();
    if (zone == null) {
        throw new RuntimeException("Could not find default timezone");
    }
    setTimeInMillis(System.currentTimeMillis());
  }

  /**
   * Gets this Calendar's current time.
   *
   * @return the current time.
   *
   * @see #setTime
   */
  public final Date getTime() {
    if (date == null)
      return date = new Date( getTimeInMillis() );
    else {
      synchronized (date) {
        date.setTime( getTimeInMillis() );
        return date;
      }
    }
  }

  /**
   * Sets this Calendar's current time with the given Date.
   * <p>
   * Note: Calling <code>setTime()</code> with
   * <code>Date(Long.MAX_VALUE)</code> or <code>Date(Long.MIN_VALUE)</code>
   * may yield incorrect field values from <code>get()</code>.
   *
   * @param date the given Date.
   *
   * @see #getTime
   */
  public final void setTime(Date date) {
    setTimeInMillis( date.getTime() );
  }

  /**
   * Gets a calendar using the default time zone and default locale.
   *
   * @return a Calendar.
   */

  /* <p>
   * The following is information for implementers. Applications should
   * not need to be aware of this or rely on it, because each 
   * implementation may do it differently:
   * <p>
   * The Calendar will look up a class the name of which includes 
   * the platform name. The class name will take the form: <p>
   *
   * <code>{classRoot}.util.{platform}.CalendarImpl</code>
   *
   * <p>
   * The classRoot is derived from the system by looking up the system
   * property "microedition.implpath".  If this property key is not
   * found or the associated class is not present then "com.sun.cldc"
   * is used.
   * <p>
   * The platform name is derived from the system by looking for the 
   * system property "microedition.platform".
   * If this property key is not found or the associated class is 
   * not present then one of two default directories are used.
   * These are called "j2me" and "j2se". If the property
   * "microedition.configuration" is non-null then "j2me" is 
   * used, otherwise "j2se" is assumed.
   *
   */
  public static synchronized Calendar getInstance() {
    if (platform == null) {
      /* Setup the platform name */

/****
      platform = System.getProperty("microedition.platform");

      if (platform == null) {
        // Work out if we are running on a J2ME system
        if (System.getProperty("microedition.configuration") != null)
          platform = "j2me";
        else
          platform = "j2se";
      }
****/

      platform = "j2me";

      /* See if there is an alternate protocol class root */
      classRoot = System.getProperty("microedition.implpath");
      if (classRoot == null) {
        classRoot = "com.sun.cldc";
      }
    }

    try {
      /* Using the platform and protocol names lookup a class to implement the connection */
      Class clazz = Class.forName(classRoot+".util."+platform+".CalendarImpl");

      /* Construct a new instance */
      return (Calendar)clazz.newInstance();
    }
    catch (Exception x) {}

    return null;
  }

  /**
   * Gets a calendar using the specified time zone and default locale.
   * @param zone the time zone to use
   * @return a Calendar.
   */
  public static synchronized Calendar getInstance(TimeZone zone) {
    Calendar cal = getInstance();
    cal.setTimeZone(zone);
    return cal;
  }

  /**
   * Gets this Calendar's current time as a long expressed in milliseconds
   * after January 1, 1970, 0:00:00 GMT (the epoch).
   *
   * @return the current time as UTC milliseconds from the epoch.
   *
   * @see #setTimeInMillis
   */
  protected long getTimeInMillis() {
    if (!millisSet) {
      calculateTime();
      millisSet = true;
    }
    return time;
  }

  /**
   * Sets this Calendar's current time from the given long value.
   * @param millis the new time in UTC milliseconds from the epoch.
   *
   * @see #getTimeInMillis
   */
  protected void setTimeInMillis( long millis ) {
    millisSet = true;
    day_field = 0;
    time = millis;
    calculateFields();
  }

  /**
   * Gets the value for a given time field.
   * @param field the given time field (either YEAR, MONTH, DATE, DAY_OF_WEEK,
   *                                    HOUR_OF_DAY, HOUR, AM_PM, MINUTE, 
   *                                    SECOND, or MILLISECOND
   * @return the value for the given time field.
   * @exception ArrayIndexOutOfBoundsException if the parameter is not
   * one of the above.
   */
  public final int get(int field) {
    switch (field) {
    case YEAR:          return packed_date >> 9;
    case MONTH:         return (packed_date >> 5) & 15;
    case DATE:          return packed_date & 31;
    case DAY_OF_WEEK: {
      if (day_field == 0) {
        getTimeInMillis();
        calculateFields();
      }
      return day_field;
    }
    case HOUR_OF_DAY:   return packed_time >> 22;
    case HOUR: {
      int hr = (packed_time >> 22) % 12;
      return hr == 0? 12 : hr;
    }
    case AM_PM:         return (packed_time >> 22) < 12? AM: PM;
    case MINUTE:        return (packed_time >> 16) & 63;
    case SECOND:        return (packed_time >> 10) & 63;
    case MILLISECOND:   return packed_time & 1023;
    }
    throw new ArrayIndexOutOfBoundsException();
  }

  /**
   * Sets the time field with the given value.
   *
   * @param field the given time field.
   * Note that the DAY_OF_WEEK field cannot be set.
   * @param value the value to be set for the given time field.
   *
   * @exception ArrayIndexOutOfBoundsException if an illegal field
   * parameter is received.
   */
  public final void set(int field, int value) {
    millisSet = false;
    day_field = 0;
    switch (field) {
    case YEAR: // 16383 = (2 to the power 14) - 1
      packed_date = (packed_date & 511) | (value << 9);
      break;
    case MONTH:
      packed_date = (packed_date & (~(15<<5))) | ((value & 15) << 5);
      break;
    case DATE:
      packed_date = (packed_date & (~31)) | (value & 31);
      break;
    case HOUR_OF_DAY:
      value = value % 24;
      packed_time = (packed_time & 4194303) | (value << 22);
      hour_12hr = am_pm_12hr = -1;
      break;
    case HOUR: {
      if (value > 12)
        value = 12;
      if (am_pm_12hr != -1) {
        if (am_pm_12hr == PM) {
          if (value != 12)
            value += 12;
        }
        else if (value == 12)
          value = 0;
        hour_12hr = am_pm_12hr = -1;
      }
      else
        hour_12hr = value;
      packed_time = (packed_time & 4194303) | (value << 22);
      break;
    }
    case AM_PM: {
      if (hour_12hr != -1) {
        if (value == PM) {
          if (hour_12hr != 12)
            hour_12hr += 12;
        }
        else if (hour_12hr == 12)
          hour_12hr = 0;
        packed_time = (packed_time & 4194303) | (hour_12hr << 22);
        hour_12hr = am_pm_12hr = -1;
      }
      else
        am_pm_12hr = value;
      break;
    }
    case MINUTE:
      packed_time = (packed_time & (~(63<<16))) | ((value & 63) << 16);
      break;
    case SECOND:
      packed_time = (packed_time & (~(63<<10))) | ((value & 63) << 10);
      break;
    case MILLISECOND:
      packed_time = (packed_time & (~1023)) | (value & 1023);
      break;
    default: throw new ArrayIndexOutOfBoundsException();
    }
    dstSet = false;
  }

  /**
   * Compares this calendar to the specified object.
   * The result is <code>true</code> if and only if the argument is
   * not <code>null</code> and is a <code>Calendar</code> object that
   * represents the same calendar as this object.
   * @param obj the object to compare with.
   * @return <code>true</code> if the objects are the same;
   * <code>false</code> otherwise.
   */
  public boolean equals(Object obj) {
    if (this == obj)
      return true;
    if (!(obj instanceof Calendar))
      return false;

    Calendar that = (Calendar)obj;

    return getTimeInMillis() == that.getTimeInMillis() && zone.equals(that.zone);
  }

  /**
   * Compares the time field records.
   * Equivalent to comparing result of conversion to UTC.
   * @param when the Calendar to be compared with this Calendar.
   * @return true if the current time of this Calendar is before
   * the time of Calendar when; false otherwise.
   */
  public boolean before(Object when) {
    return (when instanceof Calendar
            && getTimeInMillis() < ((Calendar)when).getTimeInMillis());
  }

  /**
   * Compares the time field records.
   * Equivalent to comparing result of conversion to UTC.
   * @param when the Calendar to be compared with this Calendar.
   * @return true if the current time of this Calendar is after
   * the time of Calendar when; false otherwise.
   */
  public boolean after(Object when) {
    return (when instanceof Calendar
            && getTimeInMillis() > ((Calendar)when).getTimeInMillis());
  }

  /**
   * Sets the time zone with the given time zone value.
   * @param value the given time zone.
   *
   * @see #getTimeZone
   */
  public void setTimeZone(TimeZone value) {
    zone = value;
    getTimeInMillis();
    calculateFields();
  }

  /**
   * Gets the time zone.
   * @return the time zone object associated with this calendar.
   *
   * @see #setTimeZone
   */
  public TimeZone getTimeZone() {
    return zone;
  }

  /////////////////////////////
  // Time => Fields computation
  /////////////////////////////

  private void calculateDstOffset() {
    if (day_field == 0) {
      getTimeInMillis();
      calculateFields();
    }
    int rawOffset = zone.getRawOffset();
    long localMillis = time + rawOffset;
    long days = (long) (localMillis / ONE_DAY);
    int millisInDay = (int) (localMillis - (days * ONE_DAY));
    if (millisInDay < 0)
      millisInDay += ONE_DAY;
    dstOffset = zone.getOffset(1,
                               packed_date >> 9,
                               (packed_date >> 5) & 15,
                               packed_date & 31,
                               day_field,
                               millisInDay) - rawOffset;
    dstSet = true;
  }

  /**
   * Converts UTC as milliseconds to time field values.
   */
  private void calculateFields() {
    int rawOffset = zone.getRawOffset();
    long localMillis = time + rawOffset;

    /* Check for very extreme values -- millis near Long.MIN_VALUE or
     * Long.MAX_VALUE.  For these values, adding the zone offset can push
     * the millis past MAX_VALUE to MIN_VALUE, or vice versa.  This produces
     * the undesirable effect that the time can wrap around at the ends,
     * yielding, for example, a Date(Long.MAX_VALUE) with a big BC year
     * (should be AD).  Handle this by pinning such values to Long.MIN_VALUE
     * or Long.MAX_VALUE. - liu 8/11/98 bug 4149677 */
    if (time > 0 && localMillis < 0 && rawOffset > 0) {
      localMillis = Long.MAX_VALUE;
    } else if (time < 0 && localMillis > 0 && rawOffset < 0) {
      localMillis = Long.MIN_VALUE;
    }

    // Time to fields takes the wall millis (Standard or DST).
    timeToFields(localMillis);

    long days = (long) (localMillis / ONE_DAY);
    int millisInDay = (int) (localMillis - (days * ONE_DAY));
    if (millisInDay < 0) millisInDay += ONE_DAY;

    // Call getOffset() to get the TimeZone offset.  The millisInDay value must
    // be standard local millis.
    dstOffset = zone.getOffset(1,
                               packed_date >> 9,
                               (packed_date >> 5) & 15,
                               packed_date & 31,
                               day_field,
                               millisInDay) - rawOffset;
    dstSet = true;

    // Adjust our millisInDay for DST, if necessary.