element.java

Beginning Java 2, SDK 1.4 Edition Exercise Code samples for this book

import java.awt.Color;
import java.awt.Shape;
import java.awt.Point;
import java.awt.Graphics2D;
import java.awt.Font;

import java.awt.geom.Line2D;
import java.awt.geom.Rectangle2D;
import java.awt.geom.Ellipse2D;
import java.awt.geom.GeneralPath;
import java.awt.geom.AffineTransform;
import java.awt.geom.PathIterator;

import java.io.*;

import java.util.Vector;

import org.w3c.dom.Document;
import org.w3c.dom.Attr;

public abstract class Element implements Serializable {
  public Element(Color color) {
    this.color = color;  
  }

  // Constructor to initialize element fields from a  DOM XML Element object
  protected Element(org.w3c.dom.Element xmlElement) {
    // Get the <color> element
    org.w3c.dom.NodeList list = xmlElement.getElementsByTagName("color");
    setElementColor((org.w3c.dom.Element)list.item(0));        // Set the color

    list = xmlElement.getElementsByTagName("position");        // Get <position>
    setElementPosition((org.w3c.dom.Element)list.item(0));     // Set the position

    angle = Double.parseDouble(xmlElement.getAttribute("angle")); // Set the angle
  }

  public Color getColor() {
    return color;  
  }

  // Set or reset highlight color
  public void setHighlighted(boolean highlighted) {
    this.highlighted = highlighted;
  }

  public Point getPosition() {  
    return position;  
  }

  protected void draw(Graphics2D g2D, Shape element) {
    g2D.setPaint(highlighted ? Color.MAGENTA : color);  // Set the element color
    AffineTransform old = g2D.getTransform();      // Save the current transform
    g2D.translate(position.x, position.y);         // Translate to position
    g2D.rotate(angle);                              // Rotate about position
    g2D.draw(element);                             // Draw the element
    g2D.setTransform(old);                         // Restore original transform
  }

  protected java.awt.Rectangle getBounds(java.awt.Rectangle bounds) { 
    AffineTransform at = AffineTransform.getTranslateInstance(position.x, 
                                                              position.y);
    at.rotate(angle);
    return at.createTransformedShape(bounds).getBounds();
  }

  public void move(int deltax, int deltay) {
    position.x += deltax;
    position.y += deltay;
  } 

  public void rotate(double angle) {  
    this.angle += angle;  
  }

  protected org.w3c.dom.Element createColorElement(Document doc) {
    org.w3c.dom.Element colorElement = doc.createElement("color");
 
    Attr attr = doc.createAttribute("R");
    attr.setValue(String.valueOf(color.getRed()));
    colorElement.setAttributeNode(attr);  

    attr = doc.createAttribute("G");
    attr.setValue(String.valueOf(color.getGreen()));
    colorElement.setAttributeNode(attr);  

    attr = doc.createAttribute("B");
    attr.setValue(String.valueOf(color.getBlue()));
    colorElement.setAttributeNode(attr);
    return colorElement;      
  }

  protected org.w3c.dom.Element createPointTypeElement(Document doc,
                                                     String name,
                                                     String xValue,
                                                     String yValue) { 
    org.w3c.dom.Element element = doc.createElement(name);

    Attr attr = doc.createAttribute("x");         // Create attribute x
    attr.setValue(xValue);                        // and set its value
    element.setAttributeNode(attr);               // Insert the x attribute   

    attr = doc.createAttribute("y");              // Create attribute y
    attr.setValue(yValue);                        // and set its value
    element.setAttributeNode(attr);               // Insert the y attribute   
    return element;              
  }

  protected org.w3c.dom.Element createPositionElement(Document doc) {
    return createPointTypeElement(doc, "position",
                                  String.valueOf(position.getX()),
                                  String.valueOf(position.getY()));
  }

  protected void setElementColor(org.w3c.dom.Element colorElement) {
      color = new Color(Integer.parseInt(colorElement.getAttribute("R")),
                        Integer.parseInt(colorElement.getAttribute("G")),
                        Integer.parseInt(colorElement.getAttribute("B")));
  }

  protected void setElementPosition(org.w3c.dom.Element posElement) {
      position = new Point(); 
      position.setLocation(Double.parseDouble(posElement.getAttribute("x")),
                           Double.parseDouble(posElement.getAttribute("y")));
  }


  public abstract java.awt.Rectangle getBounds();
  public abstract void modify(Point start, Point last);
  public abstract void draw(Graphics2D g2D);
  public abstract void addElementNode(Document document);
    
  protected Color color;                             // Color of a shape
  protected boolean highlighted = false;         // Highlight flag
  final static Point origin = new Point();         // Point 0,0
  protected Point position;                        // Element position
  protected double angle = 0.0;            // Rotation angle
  
  // Nested class defining a line
  public static class Line extends Element {
    public Line(Point start, Point end, Color color) {
      super(color);
      position = start;
      line = new Line2D.Double(origin, new Point(end.x - position.x, 
                                                 end.y - position.y));
    }

    // Create a Element.Line object from a DOM Element
    // Content is <color>, <position>, <endpoint> elements. Attribute is angle.
    public Line(org.w3c.dom.Element xmlElement) {
      super(xmlElement);

      org.w3c.dom.NodeList list = xmlElement.getElementsByTagName("endpoint");
      org.w3c.dom.Element endpoint = (org.w3c.dom.Element)list.item(0);
      line = new Line2D.Double(origin.x, origin.y,
                Double.parseDouble(endpoint.getAttribute("x"))-position.getX(), 
                Double.parseDouble(endpoint.getAttribute("y"))-position.getY());
    }    

    public java.awt.Rectangle getBounds() {
      return getBounds(line.getBounds());    
    }

    public void modify(Point start, Point last) {
      line.x2 = last.x - position.x;
      line.y2 = last.y - position.y;
    }

    public void draw(Graphics2D g2D)  {
      draw(g2D, line);                              // Call base draw method
    }

    private void writeObject(ObjectOutputStream out) throws IOException {
      out.writeDouble(line.x2);
      out.writeDouble(line.y2);
    }

    private void readObject(java.io.ObjectInputStream in)
                 throws IOException, ClassNotFoundException {
      double x2 = in.readDouble();
      double y2 = in.readDouble();
      line = new Line2D.Double(0,0,x2,y2);
    }

    public void addElementNode(Document doc) {
      org.w3c.dom.Element lineElement = doc.createElement("line");
 
      // Create the angle attribute and attach it to the <line> node
      Attr attr = doc.createAttribute("angle");
      attr.setValue(String.valueOf(angle));
      lineElement.setAttributeNode(attr);
  
      // Append the <color>, <position>, and <endpoint> nodes as children
      lineElement.appendChild(createColorElement(doc));
      lineElement.appendChild(createPositionElement(doc));
      lineElement.appendChild(createEndpointElement(doc));
  
      // Append the <line> node to the document root node
      doc.getDocumentElement().appendChild(lineElement); 
    } 

    private org.w3c.dom.Element createEndpointElement(Document doc) {
      return createPointTypeElement(doc, "endpoint",
                                String.valueOf(line.x2+position.x),
                                String.valueOf(line.y2+position.y));
    }

    private Line2D.Double line;
  }

  // Nested class defining a rectangle
  public static class Rectangle extends Element {
    public Rectangle(Point start, Point end, Color color) {
      super(color);
      position = new Point(Math.min(start.x, end.x),
                           Math.min(start.y, end.y));
      rectangle = new Rectangle2D.Double(origin.x,
                                         origin.y,
                                         Math.abs(start.x - end.x),     // Width
                                         Math.abs(start.y - end.y));    // & height 
    }

    // Create a Element.Rectangle object from a DOM Element
    // Rectangle has angle attribute. Content is <color>,<position>,<bottomright>
    public Rectangle(org.w3c.dom.Element xmlElement) {
      super(xmlElement);

      org.w3c.dom.NodeList list = xmlElement.getElementsByTagName("bottomright");
      org.w3c.dom.Element bottomright = (org.w3c.dom.Element)list.item(0);
      rectangle = new Rectangle2D.Double(origin.x, origin.y, 
             Double.parseDouble(bottomright.getAttribute("x"))-position.getX(), 
             Double.parseDouble(bottomright.getAttribute("y"))-position.getY());
  }

    public java.awt.Rectangle getBounds() { 
      return getBounds(rectangle.getBounds());  
    }

    public void modify(Point start, Point last) {
      position.x = Math.min(start.x, last.x);
      position.y = Math.min(start.y, last.y);
      rectangle.width = Math.abs(start.x - last.x);
      rectangle.height = Math.abs(start.y - last.y);
    }

    public void draw(Graphics2D g2D)  {
      draw(g2D, rectangle);                              // Call base draw method    
    }

    private void writeObject(ObjectOutputStream out) throws IOException {
      out.writeDouble(rectangle.width);
      out.writeDouble(rectangle.height);
    }

    private void readObject(ObjectInputStream in)
                 throws IOException, ClassNotFoundException {
      double width = in.readDouble();
      double height = in.readDouble();
      rectangle = new Rectangle2D.Double(0,0,width,height);
    }

    public void addElementNode(Document doc) {
      org.w3c.dom.Element rectElement = doc.createElement("rectangle");
 
      // Create the angle attribute and attach it to the <rectangle> node
      Attr attr = doc.createAttribute("angle");
      attr.setValue(String.valueOf(angle));
      rectElement.setAttributeNode(attr);
 
      // Append the <color>, <position>, and <bottomright> nodes as children
      rectElement.appendChild(createColorElement(doc));
      rectElement.appendChild(createPositionElement(doc));
      rectElement.appendChild(createBottomrightElement(doc));
 
      doc.getDocumentElement().appendChild(rectElement);
    }

    private org.w3c.dom.Element createBottomrightElement(Document doc) {
      return createPointTypeElement(doc, "bottomright",
                                String.valueOf(rectangle.width+position.x),
                                String.valueOf(rectangle.height+position.y));
    }

    private Rectangle2D.Double rectangle;
  }

  // Nested class defining a circle
  public static class Circle extends Element {
    public Circle(Point center, Point circum, Color color) {
      super(color);
  
      // Radius is distance from center to circumference
      double radius = center.distance(circum);
      position = new Point(center.x - (int)radius,
                           center.y - (int)radius);
      
      circle = new Ellipse2D.Double(origin.x, origin.y,     // Position - top-left
                                    2.*radius, 2.*radius ); // Width & height

    }

    // Create a Element.Circle object from a DOM Element
    // Circle has radius, angle attributes. Content is <color>, <position>
    public Circle(org.w3c.dom.Element xmlElement) {
      super(xmlElement);
      
      double radius = Double.parseDouble(xmlElement.getAttribute("radius")); 
      circle = new Ellipse2D.Double(origin.x, origin.y,     // Position - top-left
                                    2.*radius, 2.*radius ); // Width & height
    }

    public java.awt.Rectangle getBounds() {