isocelestriangle.java

源码为科学出版社出版的英文<java设计模式>(影印版)所用的所有例子程序

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

//swing classes
import javax.swing.text.*;
import javax.swing.*;
import javax.swing.event.*;

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