package org.apache.lucene.document;
/**
* Copyright 2004 The Apache Software Foundation
*
* 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.
*/
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,
* which makes them suitable for use as field values and search terms.
*
* <P>
* 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 <code>yyyy-mm-dd hh:mm:ss</code>
* (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.
*
* <P>
* Note: dates before 1970 cannot be used, and therefore cannot be
* indexed when using this class.
*/
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.
* @throws RuntimeException if the date specified in the
* method argument is before 1970
*/
public static String dateToString(Date date) {
return timeToString(date.getTime());
}
/**
* 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
*/
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");
// 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;
}
/** 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));
}
}
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