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Java example source code file (NestedLoops.java)

This example Java source code file (NestedLoops.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

arraylist, intervalsset, iterator, line, mathillegalargumentexception, nestedloops, polygonsset, regionfactory, subline, util, vector2d

The NestedLoops.java Java example source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math3.geometry.euclidean.twod;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.apache.commons.math3.exception.MathIllegalArgumentException;
import org.apache.commons.math3.exception.util.LocalizedFormats;
import org.apache.commons.math3.geometry.Point;
import org.apache.commons.math3.geometry.euclidean.oned.IntervalsSet;
import org.apache.commons.math3.geometry.partitioning.Region;
import org.apache.commons.math3.geometry.partitioning.RegionFactory;
import org.apache.commons.math3.geometry.partitioning.SubHyperplane;

/** This class represent a tree of nested 2D boundary loops.

 * <p>This class is used for piecewise polygons construction.
 * Polygons are built using the outline edges as
 * representative of boundaries, the orientation of these lines are
 * meaningful. However, we want to allow the user to specify its
 * outline loops without having to take care of this orientation. This
 * class is devoted to correct mis-oriented loops.<p>

 * <p>Orientation is computed assuming the piecewise polygon is finite,
 * i.e. the outermost loops have their exterior side facing points at
 * infinity, and hence are oriented counter-clockwise. The orientation of
 * internal loops is computed as the reverse of the orientation of
 * their immediate surrounding loop.</p>

 * @since 3.0
 */
class NestedLoops {

    /** Boundary loop. */
    private Vector2D[] loop;

    /** Surrounded loops. */
    private List<NestedLoops> surrounded;

    /** Polygon enclosing a finite region. */
    private Region<Euclidean2D> polygon;

    /** Indicator for original loop orientation. */
    private boolean originalIsClockwise;

    /** Tolerance below which points are considered identical. */
    private final double tolerance;

    /** Simple Constructor.
     * <p>Build an empty tree of nested loops. This instance will become
     * the root node of a complete tree, it is not associated with any
     * loop by itself, the outermost loops are in the root tree child
     * nodes.</p>
     * @param tolerance tolerance below which points are considered identical
     * @since 3.3
     */
    NestedLoops(final double tolerance) {
        this.surrounded = new ArrayList<NestedLoops>();
        this.tolerance  = tolerance;
    }

    /** Constructor.
     * <p>Build a tree node with neither parent nor children

* @param loop boundary loop (will be reversed in place if needed) * @param tolerance tolerance below which points are considered identical * @exception MathIllegalArgumentException if an outline has an open boundary loop * @since 3.3 */ private NestedLoops(final Vector2D[] loop, final double tolerance) throws MathIllegalArgumentException { if (loop[0] == null) { throw new MathIllegalArgumentException(LocalizedFormats.OUTLINE_BOUNDARY_LOOP_OPEN); } this.loop = loop; this.surrounded = new ArrayList<NestedLoops>(); this.tolerance = tolerance; // build the polygon defined by the loop final ArrayList<SubHyperplane edges = new ArrayList>(); Vector2D current = loop[loop.length - 1]; for (int i = 0; i < loop.length; ++i) { final Vector2D previous = current; current = loop[i]; final Line line = new Line(previous, current, tolerance); final IntervalsSet region = new IntervalsSet(line.toSubSpace((Point<Euclidean2D>) previous).getX(), line.toSubSpace((Point<Euclidean2D>) current).getX(), tolerance); edges.add(new SubLine(line, region)); } polygon = new PolygonsSet(edges, tolerance); // ensure the polygon encloses a finite region of the plane if (Double.isInfinite(polygon.getSize())) { polygon = new RegionFactory<Euclidean2D>().getComplement(polygon); originalIsClockwise = false; } else { originalIsClockwise = true; } } /** Add a loop in a tree. * @param bLoop boundary loop (will be reversed in place if needed) * @exception MathIllegalArgumentException if an outline has crossing * boundary loops or open boundary loops */ public void add(final Vector2D[] bLoop) throws MathIllegalArgumentException { add(new NestedLoops(bLoop, tolerance)); } /** Add a loop in a tree. * @param node boundary loop (will be reversed in place if needed) * @exception MathIllegalArgumentException if an outline has boundary * loops that cross each other */ private void add(final NestedLoops node) throws MathIllegalArgumentException { // check if we can go deeper in the tree for (final NestedLoops child : surrounded) { if (child.polygon.contains(node.polygon)) { child.add(node); return; } } // check if we can absorb some of the instance children for (final Iterator<NestedLoops> iterator = surrounded.iterator(); iterator.hasNext();) { final NestedLoops child = iterator.next(); if (node.polygon.contains(child.polygon)) { node.surrounded.add(child); iterator.remove(); } } // we should be separate from the remaining children RegionFactory<Euclidean2D> factory = new RegionFactory(); for (final NestedLoops child : surrounded) { if (!factory.intersection(node.polygon, child.polygon).isEmpty()) { throw new MathIllegalArgumentException(LocalizedFormats.CROSSING_BOUNDARY_LOOPS); } } surrounded.add(node); } /** Correct the orientation of the loops contained in the tree. * <p>This is this method that really inverts the loops that where * provided through the {@link #add(Vector2D[]) add} method if * they are mis-oriented</p> */ public void correctOrientation() { for (NestedLoops child : surrounded) { child.setClockWise(true); } } /** Set the loop orientation. * @param clockwise if true, the loop should be set to clockwise * orientation */ private void setClockWise(final boolean clockwise) { if (originalIsClockwise ^ clockwise) { // we need to inverse the original loop int min = -1; int max = loop.length; while (++min < --max) { final Vector2D tmp = loop[min]; loop[min] = loop[max]; loop[max] = tmp; } } // go deeper in the tree for (final NestedLoops child : surrounded) { child.setClockWise(!clockwise); } } }

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