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;
}
}