Polygon.java

package com.bioxx.jmapgen.com.nodename.geom;

import java.util.Vector;

import com.bioxx.jmapgen.Point;


	public final class Polygon
	{
		private Vector<Point> _vertices;

		public Polygon(Vector<Point> vertices)
		{
			_vertices = vertices;
		}

		public double area()
		{
			return Math.abs(signedDoubleArea() * 0.5);
		}

		public Winding winding()
		{
			double signedDoubleArea = signedDoubleArea();
			if (signedDoubleArea < 0)
			{
				return Winding.CLOCKWISE;
			}
			if (signedDoubleArea > 0)
			{
				return Winding.COUNTERCLOCKWISE;
			}
			return Winding.NONE;
		}

		private double signedDoubleArea()
		{
			int index, nextIndex;
			int n = _vertices.size();
			Point point, next;
			double signedDoubleArea = 0;
			for (index = 0; index < n; ++index)
			{
				nextIndex = (index + 1) % n;
				point = _vertices.get(index);
				next = _vertices.get(nextIndex);
				signedDoubleArea += point.x * next.y - next.x * point.y;
			}
			return signedDoubleArea;
		}
	}