GeoHash

package com.entity;
import java.util.ArrayList;  
import java.util.Arrays;  
import java.util.HashMap;  
import java.util.List;  
  
    
public class GeoHash {  
    private LocationBean location;  
    private int hashLength = 8; //经纬度转化为geohash长度  
    private int latLength = 20; //纬度转化为二进制长度  
    private int lngLength = 20; //经度转化为二进制长度  
      
    private double minLat;//每格纬度的单位大小  
    private double minLng;//每个经度的单位大小  
    private static final char[] CHARS = {‘0‘, ‘1‘, ‘2‘, ‘3‘, ‘4‘, ‘5‘, ‘6‘, ‘7‘,   
                ‘8‘, ‘9‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘, ‘f‘, ‘g‘, ‘h‘, ‘j‘, ‘k‘, ‘m‘, ‘n‘,   
                ‘p‘, ‘q‘, ‘r‘, ‘s‘, ‘t‘, ‘u‘, ‘v‘, ‘w‘, ‘x‘, ‘y‘, ‘z‘};  
    private static HashMap<Character, Integer> CHARSMAP;  
      
    static {  
        CHARSMAP = new HashMap<Character, Integer>();  
        for (int i = 0; i < CHARS.length; i++) {  
            CHARSMAP.put(CHARS[i], i);  
        }  
    }  
      
    public GeoHash(double lat, double lng) {  
        location = new LocationBean(lat, lng);  
        setMinLatLng();  
    }  
      
    public int gethashLength() {  
        return hashLength;  
    }  
      
    /** 
     * @Author:lulei   
     * @Description: 设置经纬度的最小单位 
     */  
    private void setMinLatLng() {  
        minLat = LocationBean.MAXLAT - LocationBean.MINLAT;  
        for (int i = 0; i < latLength; i++) {  
            minLat /= 2.0;  
        }  
        minLng = LocationBean.MAXLNG - LocationBean.MINLNG;  
        for (int i = 0; i < lngLength; i++) {  
            minLng /= 2.0;  
        }  
    }  
      
    /** 
     * @return 
     * @Author:lulei   
     * @Description: 求所在坐标点及周围点组成的九个 
     */  
    public List<String> getGeoHashBase32For9() {  
        double leftLat = location.getLat() - minLat;  
        double rightLat = location.getLat() + minLat;  
        double upLng = location.getLng() - minLng;  
        double downLng = location.getLng() + minLng;  
        List<String> base32For9 = new ArrayList<String>();  
        //左侧从上到下 3个  
        String leftUp = getGeoHashBase32(leftLat, upLng);  
        if (!(leftUp == null || "".equals(leftUp))) {  
            base32For9.add(leftUp);  
        }  
        String leftMid = getGeoHashBase32(leftLat, location.getLng());  
        if (!(leftMid == null || "".equals(leftMid))) {  
            base32For9.add(leftMid);  
        }  
        String leftDown = getGeoHashBase32(leftLat, downLng);  
        if (!(leftDown == null || "".equals(leftDown))) {  
            base32For9.add(leftDown);  
        }  
        //中间从上到下 3个  
        String midUp = getGeoHashBase32(location.getLat(), upLng);  
        if (!(midUp == null || "".equals(midUp))) {  
            base32For9.add(midUp);  
        }  
        String midMid = getGeoHashBase32(location.getLat(), location.getLng());  
        if (!(midMid == null || "".equals(midMid))) {  
            base32For9.add(midMid);  
        }  
        String midDown = getGeoHashBase32(location.getLat(), downLng);  
        if (!(midDown == null || "".equals(midDown))) {  
            base32For9.add(midDown);  
        }  
        //右侧从上到下 3个  
        String rightUp = getGeoHashBase32(rightLat, upLng);  
        if (!(rightUp == null || "".equals(rightUp))) {  
            base32For9.add(rightUp);  
        }  
        String rightMid = getGeoHashBase32(rightLat, location.getLng());  
        if (!(rightMid == null || "".equals(rightMid))) {  
            base32For9.add(rightMid);  
        }  
        String rightDown = getGeoHashBase32(rightLat, downLng);  
        if (!(rightDown == null || "".equals(rightDown))) {  
            base32For9.add(rightDown);  
        }  
        return base32For9;  
    }  
  
    /** 
     * @param length 
     * @return 
     * @Author:lulei   
     * @Description: 设置经纬度转化为geohash长度 
     */  
    public boolean sethashLength(int length) {  
        if (length < 1) {  
            return false;  
        }  
        hashLength = length;  
        latLength = (length * 5) / 2;  
        if (length % 2 == 0) {  
            lngLength = latLength;  
        } else {  
            lngLength = latLength + 1;  
        }  
        setMinLatLng();  
        return true;  
    }  
      
    /** 
     * @return 
     * @Author:lulei   
     * @Description: 获取经纬度的base32字符串 
     */  
    public String getGeoHashBase32() {  
        return getGeoHashBase32(location.getLat(), location.getLng());  
    }  
      
    /** 
     * @param lat 
     * @param lng 
     * @return 
     * @Author:lulei   
     * @Description: 获取经纬度的base32字符串 
     */  
    private String getGeoHashBase32(double lat, double lng) {  
        boolean[] bools = getGeoBinary(lat, lng);  
        if (bools == null) {  
            return null;  
        }  
        StringBuffer sb = new StringBuffer();  
        for (int i = 0; i < bools.length; i = i + 5) {  
            boolean[] base32 = new boolean[5];  
            for (int j = 0; j < 5; j++) {  
                base32[j] = bools[i + j];  
            }  
            char cha = getBase32Char(base32);  
            if (‘ ‘ == cha) {  
                return null;  
            }  
            sb.append(cha);  
        }  
        return sb.toString();  
    }  
      
    /** 
     * @param base32 
     * @return 
     * @Author:lulei   
     * @Description: 将五位二进制转化为base32 
     */  
    private char getBase32Char(boolean[] base32) {  
        if (base32 == null || base32.length != 5) {  
            return ‘ ‘;  
        }  
        int num = 0;  
        for (boolean bool : base32) {  
            num <<= 1;  
            if (bool) {  
                num += 1;  
            }  
        }  
        return CHARS[num % CHARS.length];  
    }  
      
    /** 
     * @param i 
     * @return 
     * @Author:lulei   
     * @Description: 将数字转化为二进制字符串 
     */  
    private String getBase32BinaryString(int i) {  
        if (i < 0 || i > 31) {  
            return null;  
        }  
        String str = Integer.toBinaryString(i + 32);  
        return str.substring(1);  
    }  
      
    /** 
     * @param geoHash 
     * @return 
     * @Author:lulei   
     * @Description: 将geoHash转化为二进制字符串 
     */  
    private String getGeoHashBinaryString(String geoHash) {  
        if (geoHash == null || "".equals(geoHash)) {  
            return null;  
        }  
        StringBuffer sb = new StringBuffer();  
        for (int i = 0; i < geoHash.length(); i++) {  
            char c = geoHash.charAt(i);  
            if (CHARSMAP.containsKey(c)) {  
                String cStr = getBase32BinaryString(CHARSMAP.get(c));  
                if (cStr != null) {  
                    sb.append(cStr);  
                }  
            }  
        }  
        return sb.toString();  
    }  
      
    /** 
     * @param geoHash 
     * @return 
     * @Author:lulei   
     * @Description: 返回geoHash 对应的坐标 
     */  
    public LocationBean getLocation(String geoHash) {  
        String geoHashBinaryStr = getGeoHashBinaryString(geoHash);  
        if (geoHashBinaryStr == null) {  
            return null;  
        }  
        StringBuffer lat = new StringBuffer();  
        StringBuffer lng = new StringBuffer();  
        for (int i = 0; i < geoHashBinaryStr.length(); i++) {  
            if (i % 2 != 0) {  
                lat.append(geoHashBinaryStr.charAt(i));  
            } else {  
                lng.append(geoHashBinaryStr.charAt(i));  
            }  
        }  
        double latValue = getGeoHashMid(lat.toString(), LocationBean.MINLAT, LocationBean.MAXLAT);  
        double lngValue = getGeoHashMid(lng.toString(), LocationBean.MINLNG, LocationBean.MAXLNG);  
        LocationBean location = new LocationBean(latValue, lngValue);  
     //   location.setGeoHash(geoHash);  
        return location;  
    }  
      
    /** 
     * @param binaryStr 
     * @param min 
     * @param max 
     * @return 
     * @Author:lulei   
     * @Description: 返回二进制对应的中间值 
     */  
    private double getGeoHashMid(String binaryStr, double min, double max) {  
        if (binaryStr == null || binaryStr.length() < 1) {  
            return (min + max) / 2.0;  
        }  
        if (binaryStr.charAt(0) == ‘1‘) {  
            return getGeoHashMid(binaryStr.substring(1), (min + max) / 2.0, max);  
        } else {  
            return getGeoHashMid(binaryStr.substring(1), min, (min + max) / 2.0);  
        }  
    }  
      
    /** 
     * @param lat 
     * @param lng 
     * @return 
     * @Author:lulei   
     * @Description: 获取坐标的geo二进制字符串 
     */  
    private boolean[] getGeoBinary(double lat, double lng) {  
        boolean[] latArray = getHashArray(lat, LocationBean.MINLAT, LocationBean.MAXLAT, latLength);  
        boolean[] lngArray = getHashArray(lng, LocationBean.MINLNG, LocationBean.MAXLNG, lngLength);  
        return merge(latArray, lngArray);  
    }  
      
    /** 
     * @param latArray 
     * @param lngArray 
     * @return 
     * @Author:lulei   
     * @Description: 合并经纬度二进制 
     */  
    private boolean[] merge(boolean[] latArray, boolean[] lngArray) {  
        if (latArray == null || lngArray == null) {  
            return null;  
        }  
        boolean[] result = new boolean[lngArray.length + latArray.length];  
        Arrays.fill(result, false);  
        for (int i = 0; i < lngArray.length; i++) {  
            result[2 * i] = lngArray[i];  
        }  
        for (int i = 0; i < latArray.length; i++) {  
            result[2 * i + 1] = latArray[i];  
        }  
        return result;  
    }  
      
    /** 
     * @param value 
     * @param min 
     * @param max 
     * @return 
     * @Author:lulei   
     * @Description: 将数字转化为geohash二进制字符串 
     */  
    private boolean[] getHashArray(double value, double min, double max, int length) {  
        if (value < min || value > max) {  
            return null;  
        }  
        if (length < 1) {  
            return null;  
        }  
        boolean[] result = new boolean[length];  
        for (int i = 0; i < length; i++) {  
            double mid = (min + max) / 2.0;  
            if (value > mid) {  
                result[i] = true;  
                min = mid;  
            } else {  
                result[i] = false;  
                max = mid;  
            }  
        }  
        return result;  
    }  
      
  
    public static void main(String[] args) {  
        // TODO Auto-generated method stub   
        GeoHash g = new GeoHash(40.221227, 116.24875);  
        String geoHash = g.getGeoHashBase32();  
        System.out.println(geoHash);  
        LocationBean bean = g.getLocation(geoHash);  
        System.out.println(bean.getLat()+"    "+ bean.getLng());  
    }  
    class LocationBean {  
        public static final double MINLAT = -90;  
        public static final double MAXLAT = 90;  
        public static final double MINLNG = -180;  
        public static final double MAXLNG = 180;  
        private double lat;//纬度[-90,90]  
        private double lng;//经度[-180,180]  
          
        public LocationBean(double lat, double lng) {  
            this.lat = lat;  
            this.lng = lng;  
        }  
        public double getLat() {  
            return lat;  
        }  
        public void setLat(double lat) {  
            this.lat = lat;  
        }  
        public double getLng() {  
            return lng;  
        }  
        public void setLng(double lng) {  
            this.lng = lng;  
        }  
    }  
}