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Lucene example source code file (DistanceHandler.java)

This example Lucene source code file (DistanceHandler.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

distancehandler, distancehandler, double, double, exact, hashmap, map, map, precision, precision, string, twentyfeet, twofeet, twohundredfeet, util

The Lucene DistanceHandler.java source code

 * 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,
 * See the License for the specific language governing permissions and
 * limitations under the License.

package org.apache.lucene.spatial.tier;

import org.apache.lucene.spatial.DistanceUtils;

import java.util.HashMap;
import java.util.Map;

 * Provide a high level access point to distances
 * Used by DistanceSortSource and DistanceQuery
 * <p>NOTE: This API is still in
 * flux and might change in incompatible ways in the next
 * release.</font>
public class DistanceHandler {

  private Map<Integer,Double> distances;
  private Map<String, Double> distanceLookupCache;
  private Precision precise;
  public DistanceHandler (Map<Integer,Double> distances, Map distanceLookupCache, Precision precise){
    this.distances = distances;
    this.distanceLookupCache = distanceLookupCache;
    this.precise = precise; 
  public static double getPrecision(double x, Precision thisPrecise){
    if(thisPrecise != null){
      double dif = 0;
      switch(thisPrecise) {
        case EXACT: return x;
        case TWOFEET:        dif = x % 0.0001; break;
        case TWENTYFEET:     dif = x % 0.001;  break;
        case TWOHUNDREDFEET: dif = x % 0.01; break;
      return x - dif;
    return x;
  public Precision getPrecision() {
    return precise;
  public double getDistance(int docid, double centerLat, double centerLng, double lat, double lng){
    // check to see if we have distances
    // if not calculate the distance
    if(distances == null){
      return DistanceUtils.getDistanceMi(centerLat, centerLng, lat, lng);
    // check to see if the doc id has a cached distance
    Double docd = distances.get( docid );
    if (docd != null){
      return docd.doubleValue();
    //check to see if we have a precision code
    // and if another lat/long has been calculated at
    // that rounded location
    if (precise != null) {
      double xLat = getPrecision(lat, precise);
      double xLng = getPrecision(lng, precise);
      String k = Double.valueOf(xLat).toString() +","+ Double.valueOf(xLng).toString();
      Double d = (distanceLookupCache.get(k));
      if (d != null){
        return d.doubleValue();
    //all else fails calculate the distances    
    return DistanceUtils.getDistanceMi(centerLat, centerLng, lat, lng);
  public static void main(String args[]){ 
    DistanceHandler db = new DistanceHandler(new HashMap<Integer,Double>(), new HashMap(), Precision.TWOHUNDREDFEET);
    System.out.println(DistanceHandler.getPrecision(-1234.123456789, db.getPrecision()));

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