Module org.apache.sis.feature
Package org.apache.sis.index.tree

Class PointTree<E>

Object
AbstractCollection<E>
AbstractSet<E>
PointTree<E>
Type Parameters:
E - the type of elements stored in this tree.
All Implemented Interfaces:
Iterable<E>, Collection<E>, Set<E>, Checked­Container<E>
public class PointTree<E> extends AbstractSet<E> implements CheckedContainer<E>
A k-dimensional tree index for points. For k=2, this is a point QuadTree. For k=3, this is a point Octree. Higher dimensions are also accepted up to 6<E> dimensions. Elements are stored in this Point­Tree as arbitrary non-null objects with their coordinates computed by a user-specified locator function. That function expects an element E in argument and returns its coordinates as a double[] array. The coordinates of each elements must be stable, i.e. applying the locator function twice on the same element must return the same coordinates. Searches based on element coordinates can be done with the following methods: The performances of this Point­Tree depends on two parameters: an estimated bounding box of the points to be added in this tree and a maximal capacity of leaf nodes (not to be confused with a capacity of the tree). More details are given in the constructor.

Thread-safety

This class is not thread-safe when the tree content is modified. But if the tree is kept unmodified after construction, then multiple read operations in concurrent threads are safe. Users can synchronize with Read­Write­Lock (the read lock must be held for complete duration of iterations or stream consumptions).

Serialization

This tree is serializable if the locator function and all elements in the tree are also serializable. However, the serialization details is implementation specific and may change in any future Apache SIS version.

Limitations

Current implementation does not yet support removal of elements.

References

Insertion algorithm is based on design of QuadTree index in H. Samet, The Design and Analysis of Spatial Data Structures. Massachusetts: Addison Wesley Publishing Company, 1989.
Since:
1.1

  • Field Details

    • MAXIMUM_DIMENSIONS

      public static final int MAXIMUM_DIMENSIONS
      The maximum number of dimensions (inclusive) that this class currently supports. Current maximum is 6. This restriction come from 2⁶ = 64.
      See Also:

  • Constructor Details

    • PointTree

      public PointTree(PointTree<E> other)
      Creates a new tree initialized to a copy of the given tree. This copy constructor shares some data structure from the other tree for reducing memory usage, but the two trees are nevertheless independent (changes in a tree does not affect the other tree).
      Parameters:
      other - the other tree to copy.

    • PointTree

      public PointTree(Class<E> elementType, Envelope bounds, PointTree.Locator<? super E> locator, int nodeCapacity, boolean parallel)
      Creates an initially empty k-dimensional tree with the given capacity for each node. The number of dimensions of the given envelope determines the number of dimensions of points in this tree. The positions computed by locator must have the same number of dimensions than the given envelope.

      The bounds argument specifies the expected region of points to be added in this Point­Tree. Those bounds do not need to be exact; Point­Tree will work even if some points are located outside those bounds. However, performances will be better if the envelope center is close to the median of the points to be inserted in the Point­Tree, and if the majority of points are inside those bounds.

      The given node­Capacity is a threshold value controlling when the content of a node should be splited into smaller children nodes. That capacity should be a relatively small number, for example 10. Determining the most efficient value may require benchmarking.

      Parameters:
      element­Type - the base type of all elements in this tree.
      bounds - bounds of the region of data to be inserted in the k-dimensional tree.
      locator - function computing the position of any element in this tree.
      node­Capacity - the capacity of each node (not to be confused with a capacity of the tree).
      parallel - whether the stream can be parallel by default. Should be false if the given locator is not thread-safe.

  • Method Details

    • getCoordinateReferenceSystem

      public final Optional<CoordinateReferenceSystem> getCoordinateReferenceSystem()
      Returns the coordinate reference system (CRS) of all points in this tree. The CRS is taken from the envelope given in argument to the constructor.
      Returns:
      the CRS of all points in this tree, if presents.
      See Also:

    • getDimension

      public final int getDimension()
      Returns the number of dimensions of points in this tree.
      Returns:
      the number of dimensions of points in this tree.
      See Also:

    • getElementType

      public final Class<E> getElementType()
      Returns the base type of all elements in this tree.
      Specified by:
      get­Element­Type in interface Checked­Container<E>
      Returns:
      the element type.

    • clear

      public void clear()
      Removes all elements from this tree.
      Specified by:
      clear in interface Collection<E>
      Specified by:
      clear in interface Set<E>
      Overrides:
      clear in class Abstract­Collection<E>

    • isEmpty

      public boolean isEmpty()
      Returns true if this set contains no elements.
      Specified by:
      is­Empty in interface Collection<E>
      Specified by:
      is­Empty in interface Set<E>
      Overrides:
      is­Empty in class Abstract­Collection<E>
      Returns:
      whether this set is empty.

    • size

      public int size()
      Returns the number of elements in this tree.
      Specified by:
      size in interface Collection<E>
      Specified by:
      size in interface Set<E>
      Specified by:
      size in class Abstract­Collection<E>
      Returns:
      the number of elements in this tree, or Integer​.MAX_VALUE if there is more elements than what an int can represent.

    • add

      public boolean add(E element)
      Inserts the specified element into this tree if it is not already present.
      Specified by:
      add in interface Collection<E>
      Specified by:
      add in interface Set<E>
      Overrides:
      add in class Abstract­Collection<E>
      Parameters:
      element - the element to insert.
      Returns:
      true if the element has been added, or false if it was already present.
      Throws:
      Null­Pointer­Exception - if the given element is null.

    • addAll

      public boolean addAll(Collection<? extends E> elements)
      Inserts all elements from the specified collection into this tree if they are not already present.
      Specified by:
      add­All in interface Collection<E>
      Specified by:
      add­All in interface Set<E>
      Overrides:
      add­All in class Abstract­Collection<E>
      Parameters:
      elements - the elements to insert.
      Returns:
      true if at least one element has been added.
      Throws:
      Null­Pointer­Exception - if an element is null.

    • contains

      public boolean contains(Object element)
      Returns true if this set contains the specified element.
      Specified by:
      contains in interface Collection<E>
      Specified by:
      contains in interface Set<E>
      Overrides:
      contains in class Abstract­Collection<E>
      Parameters:
      element - the object to search.
      Returns:
      whether this set contains the specified element.

    • iterator

      public Iterator<E> iterator()
      Creates an iterator over all elements in this set. In current implementation, the iterator does not support element removal.
      Specified by:
      iterator in interface Collection<E>
      Specified by:
      iterator in interface Iterable<E>
      Specified by:
      iterator in interface Set<E>
      Specified by:
      iterator in class Abstract­Collection<E>

    • spliterator

      public Spliterator<E> spliterator()
      Creates an iterator over all elements in this set. The iterator characteristics are sized, distinct and non-null.
      Specified by:
      spliterator in interface Collection<E>
      Specified by:
      spliterator in interface Iterable<E>
      Specified by:
      spliterator in interface Set<E>

    • parallelStream

      public Stream<E> parallelStream()
      Returns a possibly parallel stream with this tree as its source. It is allowable for this method to return a sequential stream.
      Specified by:
      parallel­Stream in interface Collection<E>
      Returns:
      a possibly parallel stream over the elements in this tree.

    • queryByBoundingBox

      public Stream<E> queryByBoundingBox(Envelope searchRegion)
      Returns all elements in the given bounding box. The given envelope shall be in the same CRS than the points in this tree (this is currently not verified). The returned stream may be parallel by default, depending on the argument given to the constructor. If the action to be applied on the stream cannot be parallel, then user should invoke Base­Stream​.sequential() explicitly.
      Parameters:
      search­Region - envelope representing the rectangular search region.
      Returns:
      elements that are in the given search region (bounds inclusive).