datefield.java

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package org.apache.lucene.document;

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import java.util.Date;

/** Provides support for converting dates to strings and vice-versa.  The
   * strings are structured so that lexicographic sorting orders by date.  This
   * makes them suitable for use as field values and search terms.  */
public class DateField {
  private DateField() {}

  // make date strings long enough to last a millenium
  private static int DATE_LEN = Long.toString(1000L*365*24*60*60*1000,
					       Character.MAX_RADIX).length();

  public static String MIN_DATE_STRING() {
    return timeToString(0);
  }

  public static String MAX_DATE_STRING() {
    char[] buffer = new char[DATE_LEN];
    char c = Character.forDigit(Character.MAX_RADIX-1, Character.MAX_RADIX);
    for (int i = 0 ; i < DATE_LEN; i++)
      buffer[i] = c;
    return new String(buffer);
  }
  
  /** Converts a Date to a string suitable for indexing. */
  public static String dateToString(Date date) {
    return timeToString(date.getTime());
  }
  /** Converts a millisecond time to a string suitable for indexing. */
  public static String timeToString(long time) {
    if (time < 0)
      throw new RuntimeException("time too early");

    String s = Long.toString(time, Character.MAX_RADIX);

    if (s.length() > DATE_LEN)
      throw new RuntimeException("time too late");

    while (s.length() < DATE_LEN)
      s = "0" + s;				  // pad with leading zeros

    return s;
  }

  /** Converts a string-encoded date into a millisecond time. */
  public static long stringToTime(String s) {
    return Long.parseLong(s, Character.MAX_RADIX);
  }
  /** Converts a string-encoded date into a Date object. */
  public static Date stringToDate(String s) {
    return new Date(stringToTime(s));
  }
}