// TwoDimFig.java
// This file gives the top-level class in an example
// that illustrates inheritance, interfaces, and
// simple graphics.

// S. Tanimoto, 10 Feb 2000.

import java.awt.*;

public abstract class TwoDimFig  
    implements SizeFunctions, Paintable {

    protected Color c;

    public abstract String describe();
    public abstract double area();
    public abstract double volume();
    public abstract int nVertices();
    public abstract int nFaces();

    public void setColor(Color c) { this.c = c; }
    public abstract void paint(Graphics g);
}

//----------------------------------------------
// SizeFunctions.java
// This file lists the protocol for the SizeFunctions interface.
// S. Tanimoto, 10 Feb 2000.

interface SizeFunctions {

    public double area();
    public double volume();
    public int nVertices();
    public int nFaces();

}
//----------------------------------------------
// Paintable.java
// This file lists the protocol for the Paintable interface.
// S. Tanimoto, 10 Feb 2000

import java.awt.*;

interface Paintable {

    public void setColor(Color c);
    public void paint(Graphics g);

}
//----------------------------------------------
// Circle.java
// This file provides the class Circle.
// S. Tanimoto, 10 Feb. 2000

import java.awt.*;

public class Circle extends TwoDimFig {

    protected double r;

    Circle(double r) { this.r = r; }
    public String describe() { return "a circle with radius " + r; }
    public int nVertices() { return 0; }
    public int nFaces() { return 1; }
    public double area() { return r * r * 3.14159; }
    public double volume() { return 0.0; }

    public void paint(Graphics g) {
        g.setColor(c);
        g.drawOval(0, 0, (int)r, (int)r);
    }
}
//----------------------------------------------
// Polygon.java
// This file provides the class Polygon.
// S. Tanimoto, 10 Feb. 2000

import java.awt.*;
import java.util.*;

public class Polygon extends TwoDimFig {

    protected Vector vertices;

    Polygon() {}
    Polygon(int n) {
        vertices = new Vector();
        int R = 100; double ANGLE = 2.0 * 3.14159 / n;
        for(int i = 0; i < n; i++) {
            Point p = new Point((int)(R + R*(Math.cos(i * ANGLE))),
                                (int)(R + R*(Math.sin(i * ANGLE))));
            vertices.addElement(p);
        }
    }

    public String describe() {
        return "a polygon with " + vertices.size() + " vertices";
    }

    public double area() {
        if (vertices.size() < 3) return 0.0;
        Enumeration enum = vertices.elements();
        Point firstVertex = (Point) enum.nextElement();
        Point lastVertex = firstVertex;
        double total = 0.0;
        while(enum.hasMoreElements()) {
            Point thisVertex = (Point) enum.nextElement();
            total += areaUnderSegment(lastVertex, thisVertex);
            lastVertex = thisVertex;
        }
        total += areaUnderSegment(lastVertex, firstVertex);
        return total;
    }

    private double areaUnderSegment(Point p1, Point p2) {
        return (p1.x - p2.x) * (p1.y + p2.y) / 2;
    }

    public double volume() { return 0.0; }
    public int nVertices() { return vertices.size(); }
    public int nFaces() { return 1; }

    public void paint(Graphics g) {
        g.setColor(c);
        Enumeration enum = vertices.elements();
        Point firstVertex = (Point) enum.nextElement();
        Point lastVertex = firstVertex;
        while(enum.hasMoreElements()) {
            Point thisVertex = (Point) enum.nextElement();
            g.drawLine(lastVertex.x, lastVertex.y , thisVertex.x, thisVertex.y);
            lastVertex = thisVertex;
        }
        g.drawLine(lastVertex.x, lastVertex.y , firstVertex.x, firstVertex.y);
    }
}
//----------------------------------------------
// Triangle.java
// This file provides the class Triangle.
// S. Tanimoto, 10 Feb. 2000

import java.awt.*;
import java.util.*;

public class Triangle extends Polygon {

    Triangle(Point p1, Point p2, Point p3) { 
        vertices = new Vector();
        vertices.addElement(p1);
        vertices.addElement(p2);
        vertices.addElement(p3);
    }

    public String describe() {
        if (isIsosceles()) return "an isosceles triangle";
        else return "a triangle";
    }

    public boolean isIsosceles() {
        Point p1 = (Point) vertices.elementAt(0);
        Point p2 = (Point) vertices.elementAt(1);
        Point p3 = (Point) vertices.elementAt(2);
        int d12 = dist(p1,p2);
        int d23 = dist(p2,p3);
        int d31 = dist(p3,p1);

        return ((d12 == d23) || (d23 == d31) || (d12 == d31));
    }

    private int dist(Point p1, Point p2) {
        return (int)((double) 
          Math.sqrt((double)(((p1.x - p2.x)*(p1.x - p2.x)) + 
               ((p1.y - p2.y)*(p1.y - p2.y)))) );
    }
}
//----------------------------------------------
// TestApplet.java
// This file provides the class TestApplet.
// S. Tanimoto, 10 Feb. 2000

import java.awt.*;
import java.util.*;
import java.applet.*;

public class TestApplet extends Applet {

   TwoDimFig f1, f2, f3;

   public void init() {

       f1 = new Circle(25.0);
       f1.setColor(Color.red);
       f2 = new Polygon(4);
       f2.setColor(Color.blue);
       f3 = new Triangle(new Point(100,100), 
                         new Point(100,200),
                         new Point(200,100));
       f3.setColor(Color.orange);

   }

   public void paint(Graphics g) {
       System.out.println("Now painting " + f1.describe() + 
           " with area " + f1.area());
       f1.paint(g);
       System.out.println("Now painting " + f2.describe() +
           " with area " + f2.area());
       f2.paint(g);
       System.out.println("Now painting " + f3.describe() +
           " with area " + f3.area());
       f3.paint(g);
   }

}
//----------------------------------------------