com.vividsolutions.jts.index.quadtree

Class Quadtree

  • All Implemented Interfaces:
    SpatialIndex, Serializable 

    public class Quadtree
extends Object
implements SpatialIndex, Serializable
    A Quadtree is a spatial index structure for efficient range querying of items bounded by 2D rectangles. Geometrys can be indexed by using their Envelopes. Any type of Object can also be indexed as long as it has an extent that can be represented by an Envelope.

    This Quadtree index provides a primary filter for range rectangle queries. The various query methods return a list of all items which may intersect the query rectangle. Note that it may thus return items which do not in fact intersect the query rectangle. A secondary filter is required to test for actual intersection between the query rectangle and the envelope of each candidate item. The secondary filter may be performed explicitly, or it may be provided implicitly by subsequent operations executed on the items (for instance, if the index query is followed by computing a spatial predicate between the query geometry and tree items, the envelope intersection check is performed automatically.

    This implementation does not require specifying the extent of the inserted items beforehand. It will automatically expand to accomodate any extent of dataset.

    This data structure is also known as an MX-CIF quadtree following the terminology of Samet and others.

    See Also:
    Serialized Form

    • Constructor Summary

      Constructors

      Constructor and Description
      Quadtree()
      Constructs a Quadtree with zero items.

    • Method Summary

      Modifier and Type Method and Description
      int depth()
      Returns the number of levels in the tree.
      static Envelope ensureExtent(Envelope itemEnv, double minExtent)
      Ensure that the envelope for the inserted item has non-zero extents.
      void insert(Envelope itemEnv, Object item)
      Adds a spatial item with an extent specified by the given Envelope to the index
      boolean isEmpty()
      Tests whether the index contains any items.
      List query(Envelope searchEnv)
      Queries the tree and returns items which may lie in the given search envelope.
      void query(Envelope searchEnv, ItemVisitor visitor)
      Queries the tree and visits items which may lie in the given search envelope.
      List queryAll()
      Return a list of all items in the Quadtree
      boolean remove(Envelope itemEnv, Object item)
      Removes a single item from the tree.
      int size()
      Returns the number of items in the tree.

    • Constructor Detail

      • Quadtree

        public Quadtree()
        Constructs a Quadtree with zero items.

    • Method Detail

      • ensureExtent

        public static Envelope ensureExtent(Envelope itemEnv,
                                    double minExtent)
        Ensure that the envelope for the inserted item has non-zero extents. Use the current minExtent to pad the envelope, if necessary

      • depth

        public int depth()
        Returns the number of levels in the tree.

      • isEmpty

        public boolean isEmpty()
        Tests whether the index contains any items.
        Returns:
        true if the index does not contain any items

      • size

        public int size()
        Returns the number of items in the tree.
        Returns:
        the number of items in the tree

      • insert

        public void insert(Envelope itemEnv,
                   Object item)
        Description copied from interface: SpatialIndex
        Adds a spatial item with an extent specified by the given Envelope to the index

      • remove

        public boolean remove(Envelope itemEnv,
                      Object item)
        Removes a single item from the tree.
        Specified by:
        remove in interface  SpatialIndex
        Parameters:
        itemEnv - the Envelope of the item to be removed
        item - the item to remove
        Returns:
        true if the item was found (and thus removed)

      • query

        public List query(Envelope searchEnv)
        Queries the tree and returns items which may lie in the given search envelope. Precisely, the items that are returned are all items in the tree whose envelope may intersect the search Envelope. Note that some items with non-intersecting envelopes may be returned as well; the client is responsible for filtering these out. In most situations there will be many items in the tree which do not intersect the search envelope and which are not returned - thus providing improved performance over a simple linear scan.
        Specified by:
        query in interface  SpatialIndex
        Parameters:
        searchEnv - the envelope of the desired query area.
        Returns:
        a List of items which may intersect the search envelope

      • query

        public void query(Envelope searchEnv,
                  ItemVisitor visitor)
        Queries the tree and visits items which may lie in the given search envelope. Precisely, the items that are visited are all items in the tree whose envelope may intersect the search Envelope. Note that some items with non-intersecting envelopes may be visited as well; the client is responsible for filtering these out. In most situations there will be many items in the tree which do not intersect the search envelope and which are not visited - thus providing improved performance over a simple linear scan.
        Specified by:
        query in interface  SpatialIndex
        Parameters:
        searchEnv - the envelope of the desired query area.
        visitor - a visitor object which is passed the visited items

      • queryAll

        public List queryAll()
        Return a list of all items in the Quadtree