/* * 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.geom; import java.util.Comparator; /** * Compares two {@link CoordinateSequence}s. * For sequences of the same dimension, the ordering is lexicographic. * Otherwise, lower dimensions are sorted before higher. * The dimensions compared can be limited; if this is done * ordinate dimensions above the limit will not be compared. * <p> * If different behaviour is required for comparing size, dimension, or * coordinate values, any or all methods can be overridden. * */ public class CoordinateSequenceComparator implements Comparator { /** * Compare two <code>double</code>s, allowing for NaN values. * NaN is treated as being less than any valid number. * * @param a a <code>double</code> * @param b a <code>double</code> * @return -1, 0, or 1 depending on whether a is less than, equal to or greater than b */ public static int compare(double a, double b) { if (a < b) return -1; if (a > b) return 1; if (Double.isNaN(a)) { if (Double.isNaN(b)) return 0; return -1; } if (Double.isNaN(b)) return 1; return 0; } /** * The number of dimensions to test */ protected int dimensionLimit; /** * Creates a comparator which will test all dimensions. */ public CoordinateSequenceComparator() { dimensionLimit = Integer.MAX_VALUE; } /** * Creates a comparator which will test only the specified number of dimensions. * * @param dimensionLimit the number of dimensions to test */ public CoordinateSequenceComparator(int dimensionLimit) { this.dimensionLimit = dimensionLimit; } /** * Compares two {@link CoordinateSequence}s for relative order. * * @param o1 a {@link CoordinateSequence} * @param o2 a {@link CoordinateSequence} * @return -1, 0, or 1 depending on whether o1 is less than, equal to, or greater than o2 */ public int compare(Object o1, Object o2) { CoordinateSequence s1 = (CoordinateSequence) o1; CoordinateSequence s2 = (CoordinateSequence) o2; int size1 = s1.size(); int size2 = s2.size(); int dim1 = s1.getDimension(); int dim2 = s2.getDimension(); int minDim = dim1; if (dim2 < minDim) minDim = dim2; boolean dimLimited = false; if (dimensionLimit <= minDim) { minDim = dimensionLimit; dimLimited = true; } // lower dimension is less than higher if (! dimLimited) { if (dim1 < dim2) return -1; if (dim1 > dim2) return 1; } // lexicographic ordering of point sequences int i = 0; while (i < size1 && i < size2) { int ptComp = compareCoordinate(s1, s2, i, minDim); if (ptComp != 0) return ptComp; i++; } if (i < size1) return 1; if (i < size2) return -1; return 0; } /** * Compares the same coordinate of two {@link CoordinateSequence}s * along the given number of dimensions. * * @param s1 a {@link CoordinateSequence} * @param s2 a {@link CoordinateSequence} * @param i the index of the coordinate to test * @param dimension the number of dimensiosn to test * @return -1, 0, or 1 depending on whether s1[i] is less than, equal to, or greater than s2[i] */ protected int compareCoordinate(CoordinateSequence s1, CoordinateSequence s2, int i, int dimension) { for (int d = 0; d < dimension; d++) { double ord1 = s1.getOrdinate(i, d); double ord2 = s2.getOrdinate(i, d); int comp = compare(ord1, ord2); if (comp != 0) return comp; } return 0; } }