Java Tutorial/2D Graphics/Polygon

Draw Polygon

import java.awt.Graphics;
import javax.swing.JComponent;
import javax.swing.JFrame;
class MyCanvas extends JComponent {
  public void paint(Graphics g) {
    int[] x = new int[]{100,200,300,400};
    int[] y = new int[]{400,300,300,100};
    g.drawPolygon (x, y, x.length);    
  }
}
public class DrawPolygon {
  public static void main(String[] a) {
    JFrame window = new JFrame();
    window.setBounds(30, 30, 300, 300);
    window.getContentPane().add(new MyCanvas());
    window.setVisible(true);
  }
}

Tests two polygons for equality. If both are null this method returns true.

/* 
 * JCommon : a free general purpose class library for the Java(tm) platform
 * 
 *
 * (C) Copyright 2000-2008, by Object Refinery Limited and Contributors.
 *
 * Project Info:  http://www.jfree.org/jcommon/index.html
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
 * USA.
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
 * in the United States and other countries.]
 *
 * -------------------
 * ShapeUtilities.java
 * -------------------
 * (C)opyright 2003-2008, by Object Refinery Limited and Contributors.
 *
 * Original Author:  David Gilbert (for Object Refinery Limited);
 * Contributor(s):   -;
 *
 * $Id: ShapeUtilities.java,v 1.18 2008/06/02 06:58:28 mungady Exp $
 *
 * Changes
 * -------
 * 13-Aug-2003 : Version 1 (DG);
 * 16-Mar-2004 : Moved rotateShape() from RefineryUtilities.java to here (DG);
 * 13-May-2004 : Added new shape creation methods (DG);
 * 30-Sep-2004 : Added createLineRegion() method (DG);
 *               Moved drawRotatedShape() method from RefineryUtilities class
 *               to this class (DG);
 * 04-Oct-2004 : Renamed ShapeUtils --> ShapeUtilities (DG);
 * 26-Oct-2004 : Added a method to test the equality of two Line2D
 *               instances (DG);
 * 10-Nov-2004 : Added new translateShape() and equal(Ellipse2D, Ellipse2D)
 *               methods (DG);
 * 11-Nov-2004 : Renamed translateShape() --> createTranslatedShape() (DG);
 * 07-Jan-2005 : Minor Javadoc fix (DG);
 * 11-Jan-2005 : Removed deprecated code in preparation for 1.0.0 release (DG);
 * 21-Jan-2005 : Modified return type of RectangleAnchor.coordinates()
 *               method (DG);
 * 22-Feb-2005 : Added equality tests for Arc2D and GeneralPath (DG);
 * 16-Mar-2005 : Fixed bug where equal(Shape, Shape) fails for two Polygon
 *               instances (DG);
 * 01-Jun-2008 : Fixed bug in equal(GeneralPath, GeneralPath) method (DG);
 *
 */
import java.awt.Shape;
import java.awt.geom.GeneralPath;
import java.awt.geom.PathIterator;
import java.util.Arrays;
/**
 * Utility methods for {@link Shape} objects.
 *
 * @author David Gilbert
 */
public class Main {
  /**
   * Tests two polygons for equality.  If both are <code>null</code> this
   * method returns <code>true</code>.
   *
   * @param p1  path 1 (<code>null</code> permitted).
   * @param p2  path 2 (<code>null</code> permitted).
   *
   * @return A boolean.
   */
  public static boolean equal(final GeneralPath p1, final GeneralPath p2) {
      if (p1 == null) {
          return (p2 == null);
      }
      if (p2 == null) {
          return false;
      }
      if (p1.getWindingRule() != p2.getWindingRule()) {
          return false;
      }
      PathIterator iterator1 = p1.getPathIterator(null);
      PathIterator iterator2 = p2.getPathIterator(null);
      double[] d1 = new double[6];
      double[] d2 = new double[6];
      boolean done = iterator1.isDone() && iterator2.isDone();
      while (!done) {
          if (iterator1.isDone() != iterator2.isDone()) {
              return false;
          }
          int seg1 = iterator1.currentSegment(d1);
          int seg2 = iterator2.currentSegment(d2);
          if (seg1 != seg2) {
              return false;
          }
          if (!Arrays.equals(d1, d2)) {
              return false;
          }
          iterator1.next();
          iterator2.next();
          done = iterator1.isDone() && iterator2.isDone();
      }
      return true;
  }
}