element.java

Java Classic Examples是我买的两本书：《JAVA经典实例》和《java入门经典源代码》里边附送光盘里带的源码

import java.awt.*;
import java.awt.geom.*;

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

  public Color getColor()
  {
    return color;
  }

  // Nested class defining a line
  public static class Line extends Element
  {
    public Line(Point start, Point end, Color color)
    {
      super(color);
      line = new Line2D.Double(start, end);
    }

    public Shape getShape()
    { 
      return line; 
    }

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

    public void modify(Point start, Point last)
    {
      line.x2 = last.x;
      line.y2 = last.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);
  //    this.start = start;                                  // Save the start point
      rectangle = new Rectangle2D.Double(
        Math.min(start.x, end.x), Math.min(start.y, end.y),    // Top-left corner
        Math.abs(start.x - end.x), Math.abs(start.y - end.y)); // Width & height
    }

    public Shape getShape()
    { 
      return rectangle; 
    }

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

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

    private Rectangle2D.Double rectangle;
 //   private Point start;
  }

  // Nested class defining a circle
  public static class Circle extends Element
  {
    public Circle(Point center, Point circum, Color color)
    {
      super(color);
  //    this.center = center;                         // Save the center point
  
      // Radius is distance from center to circumference
      double radius = center.distance(circum);

      circle = new Ellipse2D.Double(center.x - radius, center.y - radius, 
                                    2.*radius, 2.*radius ); 
    }

    public Shape getShape()
    { 
      return circle; 
    }

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

    public void modify(Point center, Point circum)
    {
      double radius = center.distance(circum);
      circle.x = center.x - (int)radius;
      circle.y = center.y - (int)radius;
      circle.width = circle.height = 2*radius;
    }

    private Ellipse2D.Double circle;
  //  private Point center;
  }

  // Nested class defining a curve
  public static class Curve extends Element
  {
    public Curve(Point start, Point next, Color color)
    {
      super(color);
      curve = new GeneralPath();
      curve.moveTo(start.x, start.y);
      curve.lineTo(next.x, next.y);
    }

    // Add another segment
    public void modify(Point start, Point next)
    {
      curve.lineTo(next.x, next.y);
    }

    public Shape getShape()
    { 
      return curve; 
    }

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

    private GeneralPath curve;
  }

  public abstract Shape getShape();
  public abstract java.awt.Rectangle getBounds();
  protected Color color;                             // Color of a shape
  public abstract void modify(Point start, Point last);
}