isocelestriangle.java

java patterns book

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

//swing classes
import com.sun.java.swing.text.*;
import com.sun.java.swing.*;
import com.sun.java.swing.event.*;

public class IsocelesTriangle extends Triangle
{
   Point newc;
   int newcx, newcy;
   int incr;

   public IsocelesTriangle(Point a, Point b, Point c)
   {
      super(a, b, c);
      double dx1 = b.x - a.x;
      double dy1 = b.y - a.y;
      double dx2 = c.x - b.x;
      double dy2 = c.y - b.y;

      double side1 = calcSide(dx1, dy1);
      double side2 = calcSide(dx2, dy2);
      
      if (side2 < side1) 
         incr = -1;
      else
         incr = 1;

      double slope = dy2 / dx2;
      double intercept = c.y - slope* c.x;
      
      //move point c so that this is an isoceles triangle
      newcx = c.x; newcy = c.y;
      while(Math.abs(side1 - side2) > 1)
      {
         newcx += incr;    //iterate a pixel at a time until close
         newcy = (int)(slope* newcx + intercept);
         dx2 = newcx - b.x;
         dy2 = newcy - b.y;
         side2 = calcSide(dx2, dy2);
      }
      newc = new Point(newcx, newcy);
   }
   //--------------------------------------
   //calculate length of side
   private double calcSide(double dx, double dy)
   {
      return Math.sqrt(dx*dx + dy*dy);
   }
   //--------------------------------------
   //draws 2nd line using saved new point
   public Point draw2ndLine(Graphics g, Point b, Point c)
   {
    g.drawLine(b.x, b.y, newc.x, newc.y);
    return newc;
   }
}