正经学徒，佛系记录，不搞事情
详细的解释交给专业的大佬，我就用用：
工具类：
包含坐标和geohash的转换；查询geohash周围九格的geohash（一个“搜索附近”功能的解决方法）
import java.util.BitSet;
import java.util.HashMap;
import java.util.Map;
public class GeoHash {
private static int numbits = 6 * 5; //经纬度单独编码长度
//32位编码对应字符
final static char[] digits = { '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' };
public static String BASE32 = "0123456789bcdefghjkmnpqrstuvwxyz";
//定义编码映射关系
final static HashMap<Character, Integer> lookup = new HashMap<Character, Integer>();
//初始化编码映射内容
static {
int i = 0;
for (char c : digits)
lookup.put(c, i++);
}
public GeoHash(){
setMap();
}
//对编码后的字符串解码
public double[] decode(String geohash) {
StringBuilder buffer = new StringBuilder();
for (char c : geohash.toCharArray()) {
int i = lookup.get(c) + 32;
buffer.append( Integer.toString(i, 2).substring(1) );
}
BitSet lonset = new BitSet();
BitSet latset = new BitSet();
//偶数位，经度
int j =0;
for (int i=0; i< numbits*2;i+=2) {
boolean isSet = false;
if ( i < buffer.length() )
isSet = buffer.charAt(i) == '1';
lonset.set(j++, isSet);
}
//奇数位，纬度
j=0;
for (int i=1; i< numbits*2;i+=2) {
boolean isSet = false;
if ( i < buffer.length() )
isSet = buffer.charAt(i) == '1';
latset.set(j++, isSet);
}
double lon = decode(lonset, -180, 180);
double lat = decode(latset, -90, 90);
return new double[] {lat, lon};
}
//根据二进制和范围解码
private double decode(BitSet bs, double floor, double ceiling) {
double mid = 0;
for (int i=0; i<bs.length(); i++) {
mid = (floor + ceiling) / 2;
if (bs.get(i))
floor = mid;
else
ceiling = mid;
}
return mid;
}
//对经纬度进行编码
public String encode(double lat, double lon) {
BitSet latbits = getBits(lat, -90, 90);
BitSet lonbits = getBits(lon, -180, 180);
StringBuilder buffer = new StringBuilder();
for (int i = 0; i < numbits; i++) {
buffer.append( (lonbits.get(i))?'1':'0');
buffer.append( (latbits.get(i))?'1':'0');
}
return base32(Long.parseLong(buffer.toString(), 2));
}
//根据经纬度和范围，获取对应二进制
private BitSet getBits(double lat, double floor, double ceiling) {
BitSet buffer = new BitSet(numbits);
for (int i = 0; i < numbits; i++) {
double mid = (floor + ceiling) / 2;
if (lat >= mid) {
buffer.set(i);
floor = mid;
} else {
ceiling = mid;
}
}
return buffer;
}
//将经纬度合并后的二进制进行指定的32位编码
private String base32(long i) {
char[] buf = new char[65];
int charPos = 64;
boolean negative = (i < 0);
if (!negative)
i = -i;
while (i <= -32) {
buf[charPos--] = digits[(int) (-(i % 32))];
i /= 32;
}
buf[charPos] = digits[(int) (-i)];
if (negative)
buf[--charPos] = '-';
return new String(buf, charPos, (65 - charPos));
}
/***********************获取九个的矩形编码****************************************/
public static Map<String, String> BORDERS = new HashMap<String, String>();
public static Map<String, String> NEIGHBORS = new HashMap<String, String>();
public static void setMap() {
NEIGHBORS.put("right:even", "bc01fg45238967deuvhjyznpkmstqrwx");
NEIGHBORS.put("left:even", "238967debc01fg45kmstqrwxuvhjyznp");
NEIGHBORS.put("top:even", "p0r21436x8zb9dcf5h7kjnmqesgutwvy");
NEIGHBORS.put("bottom:even", "14365h7k9dcfesgujnmqp0r2twvyx8zb");
NEIGHBORS.put("right:odd", "p0r21436x8zb9dcf5h7kjnmqesgutwvy");
NEIGHBORS.put("left:odd", "14365h7k9dcfesgujnmqp0r2twvyx8zb");
NEIGHBORS.put("top:odd", "bc01fg45238967deuvhjyznpkmstqrwx");
NEIGHBORS.put("bottom:odd", "238967debc01fg45kmstqrwxuvhjyznp");
BORDERS.put("right:even", "bcfguvyz");
BORDERS.put("left:even", "0145hjnp");
BORDERS.put("top:even", "prxz");
BORDERS.put("bottom:even", "028b");
BORDERS.put("right:odd", "prxz");
BORDERS.put("left:odd", "028b");
BORDERS.put("top:odd", "bcfguvyz");
BORDERS.put("bottom:odd", "0145hjnp");
}
/**获取九个点的矩形编码
* @param geohash
* @return
*/
public static String[] getGeoHashExpand(String geohash){
try {
System.out.println("========= "+geohash);
String geohashTop = calculateAdjacent(geohash, "top");
System.out.println("========= "+geohashTop);
String geohashBottom = calculateAdjacent(geohash, "bottom");
System.out.println("========= "+geohashBottom);
String geohashRight = calculateAdjacent(geohash, "right");
System.out.println("========= "+geohashRight);
String geohashLeft = calculateAdjacent(geohash, "left");
System.out.println("========= "+geohashLeft);
String geohashTopLeft = calculateAdjacent(geohashLeft, "top");
System.out.println("========= "+geohashTopLeft);
String geohashTopRight = calculateAdjacent(geohashRight, "top");
System.out.println("========= "+geohashTopRight);
String geohashBottomRight = calculateAdjacent(geohashRight, "bottom");
System.out.println("========= "+geohashBottomRight);
String geohashBottomLeft = calculateAdjacent(geohashLeft, "bottom");
System.out.println("========= "+geohashBottomLeft);
String[] expand = {geohash, geohashTop, geohashBottom, geohashRight, geohashLeft, geohashTopLeft, geohashTopRight, geohashBottomRight, geohashBottomLeft};
return expand;
} catch (Exception e) {
System.out.println(e.getMessage());
return null;
}
}
/**分别计算每个点的矩形编码
* @param srcHash
* @param dir
* @return
*/
public static String calculateAdjacent(String srcHash, String dir) {
srcHash = srcHash.toLowerCase();
char lastChr = srcHash.charAt(srcHash.length()-1);
int a = srcHash.length()%2;
String type = (a>0)?"odd":"even";
String base = srcHash.substring(0,srcHash.length()-1);
if (BORDERS.get(dir+":"+type).indexOf(lastChr)!=-1){
base = calculateAdjacent(base, dir);
}
base = base + BASE32.toCharArray()[(NEIGHBORS.get(dir+":"+type).indexOf(lastChr))];
return base;
}
public static void main(String[] args) throws Exception{
GeoHash geohash = new GeoHash();
String s = geohash.encode(45, 125);
System.out.println(s);
double[] geo = geohash.decode(s);
System.out.println(geo[0]+" "+geo[1]);
String[] points = getGeoHashExpand(s);
}
}