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JTS Topology Suite 1.14 with additional functions for GeoSpark
There is a newer version: 0.1.4

/*
 * The JTS Topology Suite is a collection of Java classes that
 * implement the fundamental operations required to validate a given
 * geo-spatial data set to a known topological specification.
 *
 * Copyright (C) 2001 Vivid Solutions
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * For more information, contact:
 *
 *     Vivid Solutions
 *     Suite #1A
 *     2328 Government Street
 *     Victoria BC  V8T 5G5
 *     Canada
 *
 *     (250)385-6040
 *     www.vividsolutions.com
 */
package com.vividsolutions.jts.index.quadtree;

import com.vividsolutions.jts.geom.Envelope;
import com.vividsolutions.jts.util.Assert;

/**
 * Represents a node of a {@link Quadtree}.  Nodes contain
 * items which have a spatial extent corresponding to the node's position
 * in the quadtree.
 *
 * @version 1.7
 */
public class Node
  extends NodeBase
{
  public static Node createNode(Envelope env)
  {
    Key key = new Key(env);
    Node node = new Node(key.getEnvelope(), key.getLevel());
    return node;
  }

  public static Node createExpanded(Node node, Envelope addEnv)
  {
    Envelope expandEnv = new Envelope(addEnv);
    if (node != null) expandEnv.expandToInclude(node.env);

    Node largerNode = createNode(expandEnv);
    if (node != null) largerNode.insertNode(node);
    return largerNode;
  }

  private Envelope env;
  private double centrex;
  private double centrey;
  private int level;

  public Node(Envelope env, int level)
  {
    //this.parent = parent;
    this.env = env;
    this.level = level;
    centrex = (env.getMinX() + env.getMaxX()) / 2;
    centrey = (env.getMinY() + env.getMaxY()) / 2;
  }

  public Envelope getEnvelope() { return env; }

  protected boolean isSearchMatch(Envelope searchEnv)
  {
    return env.intersects(searchEnv);
  }

  /**
   * Returns the subquad containing the envelope searchEnv.
   * Creates the subquad if
   * it does not already exist.
   * 
   * @return the subquad containing the search envelope
   */
  public Node getNode(Envelope searchEnv)
  {
    int subnodeIndex = getSubnodeIndex(searchEnv, centrex, centrey);
    // if subquadIndex is -1 searchEnv is not contained in a subquad
    if (subnodeIndex != -1) {
      // create the quad if it does not exist
      Node node = getSubnode(subnodeIndex);
      // recursively search the found/created quad
      return node.getNode(searchEnv);
    }
    else {
      return this;
    }
  }

  /**
   * Returns the smallest existing
   * node containing the envelope.
   */
  public NodeBase find(Envelope searchEnv)
  {
    int subnodeIndex = getSubnodeIndex(searchEnv, centrex, centrey);
    if (subnodeIndex == -1)
      return this;
    if (subnode[subnodeIndex] != null) {
      // query lies in subquad, so search it
      Node node = subnode[subnodeIndex];
      return node.find(searchEnv);
    }
    // no existing subquad, so return this one anyway
    return this;
  }

  void insertNode(Node node)
  {
    Assert.isTrue(env == null || env.contains(node.env));
//System.out.println(env);
//System.out.println(quad.env);
    int index = getSubnodeIndex(node.env, centrex, centrey);
//System.out.println(index);
    if (node.level == level - 1) {
      subnode[index] = node;
//System.out.println("inserted");
    }
    else {
      // the quad is not a direct child, so make a new child quad to contain it
      // and recursively insert the quad
      Node childNode = createSubnode(index);
      childNode.insertNode(node);
      subnode[index] = childNode;
    }
  }

  /**
   * get the subquad for the index.
   * If it doesn't exist, create it
   */
  private Node getSubnode(int index)
  {
    if (subnode[index] == null) {
      subnode[index] = createSubnode(index);
    }
    return subnode[index];
  }

  private Node createSubnode(int index)
  {
        // create a new subquad in the appropriate quadrant

      double minx = 0.0;
      double maxx = 0.0;
      double miny = 0.0;
      double maxy = 0.0;

      switch (index) {
      case 0:
        minx = env.getMinX();
        maxx = centrex;
        miny = env.getMinY();
        maxy = centrey;
        break;
      case 1:
        minx = centrex;
        maxx = env.getMaxX();
        miny = env.getMinY();
        maxy = centrey;
        break;
      case 2:
        minx = env.getMinX();
        maxx = centrex;
        miny = centrey;
        maxy = env.getMaxY();
        break;
      case 3:
        minx = centrex;
        maxx = env.getMaxX();
        miny = centrey;
        maxy = env.getMaxY();
        break;
      }
      Envelope sqEnv = new Envelope(minx, maxx, miny, maxy);
      Node node = new Node(sqEnv, level - 1);
    return node;
  }

}