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Lucene example source code file (DateField.java)

This example Lucene source code file (DateField.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

date, date, date_len, date_len, datefield, datefield, deprecated, max_date_string, min_date_string, runtimeexception, string, string, stringbuilder, util

The Lucene DateField.java source code

package org.apache.lucene.document;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.lucene.search.PrefixQuery;
import org.apache.lucene.search.TermRangeQuery;
import org.apache.lucene.search.NumericRangeQuery; // for javadocs
import org.apache.lucene.util.NumericUtils; // for javadocs

import java.util.Date;   // for javadoc
import java.util.Calendar;   // for javadoc

// do not remove in 3.0, needed for reading old indexes!

/**
 * 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 this class saves dates with millisecond granularity,
 * which is bad for {@link TermRangeQuery} and {@link PrefixQuery}, as those
 * queries are expanded to a BooleanQuery with a potentially large number
 * of terms when searching. Thus you might want to use
 * {@link DateTools} instead.
 *
 * <P>
 * Note: dates before 1970 cannot be used, and therefore cannot be
 * indexed when using this class. See {@link DateTools} for an
 * alternative without such a limitation.
 *
 * <P>
 * Another approach is {@link NumericUtils}, which provides
 * a sortable binary representation (prefix encoded) of numeric values, which
 * date/time are.
 * For indexing a {@link Date} or {@link Calendar}, just get the unix timestamp as
 * <code>long using {@link Date#getTime} or {@link Calendar#getTimeInMillis} and
 * index this as a numeric value with {@link NumericField}
 * and use {@link NumericRangeQuery} to query it.
 *
 * @deprecated If you build a new index, use {@link DateTools} or 
 * {@link NumericField} instead.
 * This class is included for use with existing
 * indices and will be removed in a future release (possibly Lucene 4.0).
 */
@Deprecated
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 '" + time + "' is too early, must be >= 0");

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

    if (s.length() > DATE_LEN)
      throw new RuntimeException("time '" + time + "' is too late, length of string " +
          "representation must be <= " + DATE_LEN);

    // Pad with leading zeros
    if (s.length() < DATE_LEN) {
      StringBuilder sb = new StringBuilder(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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