FileDocCategorySizeDatePackage
DateField.javaAPI DocApache Lucene 1.4.33415Fri May 14 14:36:26 BST 2004org.apache.lucene.document

DateField

public class DateField extends Object
Provides support for converting dates to strings and vice-versa. The strings are structured so that lexicographic sorting orders by date, which makes them suitable for use as field values and search terms.

Note that you do not have to use this class, you can just save your dates as strings if lexicographic sorting orders them by date. This is the case for example for dates like yyyy-mm-dd hh:mm:ss (of course you can leave out the delimiter characters to save some space). The advantage with using such a format is that you can easily save dates with the required granularity, e.g. leaving out seconds. This saves memory when searching with a RangeQuery or PrefixQuery, as Lucene expands these queries to a BooleanQuery with potentially very many terms.

Note: dates before 1970 cannot be used, and therefore cannot be indexed when using this class.

Fields Summary
private static int
DATE_LEN
Constructors Summary
private DateField()

Methods Summary
public static java.lang.StringMAX_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);
  
public static java.lang.StringMIN_DATE_STRING()

      
    return timeToString(0);
  
public static java.lang.StringdateToString(java.util.Date date)
Converts a Date to a string suitable for indexing.
throws
RuntimeException if the date specified in the
method argument is before 1970
    return timeToString(date.getTime());
  
public static java.util.DatestringToDate(java.lang.String s)
Converts a string-encoded date into a Date object.
    return new Date(stringToTime(s));
  
public static longstringToTime(java.lang.String s)
Converts a string-encoded date into a millisecond time.
    return Long.parseLong(s, Character.MAX_RADIX);
  
public static java.lang.StringtimeToString(long time)
Converts a millisecond time to a string suitable for indexing.
throws
RuntimeException if the time specified in the
method argument is negative, that is, before 1970
    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");

    // Pad with leading zeros
    if (s.length() < DATE_LEN) {
      StringBuffer sb = new StringBuffer(s);
      while (sb.length() < DATE_LEN)
        sb.insert(0, 0);
      s = sb.toString();
    }

    return s;