Lucene example source code file (NumberTools.java)

This example Lucene source code file (NumberTools.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

deprecated, min_string_value, negative_prefix, negative_prefix, numberformatexception, numbertools, positive_prefix, positive_prefix, radix, radix, str_size, string, string, stringbuilder

The Lucene NumberTools.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.document.NumericField; // for javadocs
import org.apache.lucene.search.NumericRangeQuery; // for javadocs
import org.apache.lucene.util.NumericUtils; // for javadocs

// do not remove this class in 3.0, it may be needed to decode old indexes!

/**
 * Provides support for converting longs to Strings, and back again. The strings
 * are structured so that lexicographic sorting order is preserved.
 * 
 * <p>
 * That is, if l1 is less than l2 for any two longs l1 and l2, then
 * NumberTools.longToString(l1) is lexicographically less than
 * NumberTools.longToString(l2). (Similarly for "greater than" and "equals".)
 * 
 * <p>
 * This class handles <b>all long values (unlike
 * {@link org.apache.lucene.document.DateField}).
 * 
 * @deprecated For new indexes use {@link NumericUtils} instead, which
 * provides a sortable binary representation (prefix encoded) of numeric
 * values.
 * To index and efficiently query numeric values use {@link NumericField}
 * and {@link NumericRangeQuery}.
 * This class is included for use with existing
 * indices and will be removed in a future release (possibly Lucene 4.0).
 */
@Deprecated
public class NumberTools {

    private static final int RADIX = 36;

    private static final char NEGATIVE_PREFIX = '-';

    // NB: NEGATIVE_PREFIX must be < POSITIVE_PREFIX
    private static final char POSITIVE_PREFIX = '0';

    //NB: this must be less than
    /**
     * Equivalent to longToString(Long.MIN_VALUE)
     */
    public static final String MIN_STRING_VALUE = NEGATIVE_PREFIX
            + "0000000000000";

    /**
     * Equivalent to longToString(Long.MAX_VALUE)
     */
    public static final String MAX_STRING_VALUE = POSITIVE_PREFIX
            + "1y2p0ij32e8e7";

    /**
     * The length of (all) strings returned by {@link #longToString}
     */
    public static final int STR_SIZE = MIN_STRING_VALUE.length();

    /**
     * Converts a long to a String suitable for indexing.
     */
    public static String longToString(long l) {

        if (l == Long.MIN_VALUE) {
            // special case, because long is not symmetric around zero
            return MIN_STRING_VALUE;
        }

        StringBuilder buf = new StringBuilder(STR_SIZE);

        if (l < 0) {
            buf.append(NEGATIVE_PREFIX);
            l = Long.MAX_VALUE + l + 1;
        } else {
            buf.append(POSITIVE_PREFIX);
        }
        String num = Long.toString(l, RADIX);

        int padLen = STR_SIZE - num.length() - buf.length();
        while (padLen-- > 0) {
            buf.append('0');
        }
        buf.append(num);

        return buf.toString();
    }

    /**
     * Converts a String that was returned by {@link #longToString} back to a
     * long.
     * 
     * @throws IllegalArgumentException
     *             if the input is null
     * @throws NumberFormatException
     *             if the input does not parse (it was not a String returned by
     *             longToString()).
     */
    public static long stringToLong(String str) {
        if (str == null) {
            throw new NullPointerException("string cannot be null");
        }
        if (str.length() != STR_SIZE) {
            throw new NumberFormatException("string is the wrong size");
        }

        if (str.equals(MIN_STRING_VALUE)) {
            return Long.MIN_VALUE;
        }

        char prefix = str.charAt(0);
        long l = Long.parseLong(str.substring(1), RADIX);

        if (prefix == POSITIVE_PREFIX) {
            // nop
        } else if (prefix == NEGATIVE_PREFIX) {
            l = l - Long.MAX_VALUE - 1;
        } else {
            throw new NumberFormatException(
                    "string does not begin with the correct prefix");
        }

        return l;
    }
}