1
我打算递归迭代循环区域内的所有网格,下面的代码将执行深度优先搜索。但是在204堆叠之后,将抛出java.lang.StackOverflowError
。stackoverflowror当通过scala处理深度优先迭代时
def geohash_circle_around_point(lat: Double, lon: Double, radius: Double) = {
def expand_neighbors_impl(ghCenter: GeoHash, ghCur: GeoHash, buffer: collection.mutable.Set[GeoHash]): Unit = {
// MARK: DP: check whether it's iterated already or not
if(buffer contains ghCur) {
return
}
buffer += ghCur
for(ghAround <- get4GeoHashAround(ghCur)) {
if(distanceBetweenGeohash(ghCenter, ghAround) <= radius) {
expand_neighbors_impl(ghCenter, ghAround, buffer)
}
}
}
def get4GeoHashAround(gh: GeoHash): Array[GeoHash] = {
Array(gh.getNorthernNeighbour, gh.getSouthernNeighbour, gh.getWesternNeighbour, gh.getEasternNeighbour)
}
def distanceBetweenGeohash(gh1: GeoHash, gh2: GeoHash) = {
haversine(gh1.getBoundingBoxCenterPoint.getLatitude, gh1.getBoundingBoxCenterPoint.getLongitude, gh2.getBoundingBoxCenterPoint.getLatitude, gh2.getBoundingBoxCenterPoint.getLongitude)
}
val ghCenter = GeoHash.withBitPrecision(lat, lon, 40)
val s = collection.mutable.Set[GeoHash]()
expand_neighbors_impl(ghCenter, ghCenter, s)
s.map(_.getBoundingBox)
}
堆栈跟踪如下:
Exception in thread "main" java.lang.StackOverflowError
at scala.collection.mutable.HashSet.index(HashSet.scala:40)
at scala.collection.mutable.FlatHashTable$class.findElemImpl(FlatHashTable.scala:126)
at scala.collection.mutable.FlatHashTable$class.containsElem(FlatHashTable.scala:121)
at scala.collection.mutable.HashSet.containsElem(HashSet.scala:40)
at scala.collection.mutable.HashSet.contains(HashSet.scala:57)
at Test$.Test$$expand_neighbors_impl$1(Test.scala:32)
at Test$$anonfun$Test$$expand_neighbors_impl$1$1.apply(Test.scala:39)
at Test$$anonfun$Test$$expand_neighbors_impl$1$1.apply(Test.scala:37)
at scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:33)
at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:186)
at Test$.Test$$expand_neighbors_impl$1(Test.scala:37)
at Test$$anonfun$Test$$expand_neighbors_impl$1$1.apply(Test.scala:39)
at Test$$anonfun$Test$$expand_neighbors_impl$1$1.apply(Test.scala:37)
at scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:33)
at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:186)
at Test$.Test$$expand_neighbors_impl$1(Test.scala:37)
....
任何人都可以给一些建议?谢谢!
P.S.
执行情况equals
和hashCode
为GeoHash
:
public boolean equals(Object obj) {
if(obj == this) {
return true;
} else {
if(obj instanceof GeoHash) {
GeoHash other = (GeoHash)obj;
if(other.significantBits == this.significantBits && other.bits == this.bits) {
return true;
}
}
return false;
}
}
public int hashCode() {
byte f = 17;
int f1 = 31 * f + (int)(this.bits^this.bits >>> 32);
f1 = 31 * f1 + this.significantBits;
return f1;
}
我相信'contains'总是返回false,因为'Geohash'没有'equals'方法吗?如果是这样的话,它会继续添加相同的对象。 –
@DarshanMehta,对于'HashSet',方法'hashCode'也是需要的。 –
@CyrilleCorpet它不言而喻.. –