Heptagons

In keeping with my strange mathematical tendencies, I decided that it would be a good idea to draw a heptagon in Java for a (would-be) simple homework assignment.

Seeing as I've obviously already worked with Java graphics and drawing (see NCSpiral!), this should be no problem, right?

It's actually a real pain since I forgot most of my trig...

But, in any case, here you go!

	import java.awt.*;
	public class Heptagon {
	private int x, y, radius;
	private double area;
	private Color theColor;
	private boolean isVisible;
	private Polygon polygon;
	/**
	* Construct a new Heptagon centered at initX, initY with a
	* color indicated by initColor. The new Heptagon is visible by
	* default.
	*
	* @param initX the x coordinate of the center of the 7-sided thingy.
	* @param initY the y coordinate of the center of the heptagon.
	* @param initRadius an arbitrary value of the distance from (initX, initY) to a point at which
	* two sides meet at roughly 5(pi)/7 radians
	* @param initColor the color of the heptagon.
	*/
	public Heptagon(int initX, int initY, int initRadius, Color initColor) {
	x = initX;
	y = initY;
	radius = initRadius;
	theColor = initColor;
	isVisible = true;
	polygon = new Polygon();
	}
	/**
	* Increases the size of the heptagon by the specified factor.
	* @param factor the amount by which you wish to increase the area of the heptagon.
	*/
	@Override
	public void scale(double factor) {
	if (factor > 0) {
	radius = (int) (Math.round(radius * factor));
	}
	}
	/**
	* Move the center of the heptagon.
	* @param newX
	* @param newY
	*/
	public void move(int newX, int newY) {
	x = newX;
	y = newY;
	polygon.reset();
	}
	/**
	* Draws the heptagon using a Graphics object.
	* Points are calculated and placed based on the radius relative
	* to the starting x and y co-ordinates using basic trigonometric functions
	* and therefore may not create a perfect regular heptagon where all sides
	* meet at 5(pi)/7 radians.
	* @param g a pointer to a pre-initialized Graphics drawing object.
	*/
	public void draw(Graphics g) {
	g.setColor(theColor);
	for (int i = 0; i < 7; i++){
	polygon.addPoint((int) (x + radius * Math.cos(i * 2 * Math.PI / 7)),
	(int) (y + radius * Math.sin(i * 2 * Math.PI / 7)));}
	g.drawPolygon(polygon);
	g.fillPolygon(polygon);
	}
	/**
	* Calculates and returns the area of the heptagon accurate to 2 decimal places
	* using the formula A = 7/4 * a^2 * cot(pi/7) where a is the length of a side
	* calculated based on the radius relative to the starting x and y co-ordinates.
	* @return area the approximate area of the heptagon, accurate to ~2 decimal places.
	*/
	public Double getArea() {
	// imagine we make points 1 and 2 from the draw() method above
	double x1 = x + radius * Math.cos(1 * 2 * Math.PI / 7);
	double x2 = x + radius * Math.cos(2 * 2 * Math.PI / 7);
	double y1 = y + radius * Math.sin(1 * 2 * Math.PI / 7);
	double y2 = y + radius * Math.sin(2 * 2 * Math.PI / 7);
	// calculate the distance between these points
	double xd = Math.abs(x1-x2);
	double yd = Math.abs(y1-y2);
	// and finally, determine the length of one side of the heptagon
	double side = Math.sqrt((Math.pow(xd, 2))+(Math.pow(yd, 2)));
	// now implement the area formula mentioned above
	area = ((7/4) * Math.pow(side, 2)) * (1/(Math.tan((Math.PI / 7))));
	return area;
	}
	/**
	* Tells you the current color being used for drawing.
	* @return theColor the current color being used for drawing.
	*/
	@Override
	public Color getColor() {
	return theColor;
	}
	/**
	* Sets a new color for drawing.
	* @param newColor the new color you wish to use.
	*/
	@Override
	public void setColor(Color newColor) {
	theColor = newColor;
	}
	/**
	* Sets the heptagon to visible or not.
	* @param visible true for visible, false for hidden.
	*/
	@Override
	public void setVisible(boolean visible) {
	isVisible = visible;
	}
	/**
	* Tells you whether the heptagon is visible.
	* @return isVisible true if visible, false if hidden.
	*/
	@Override
	public boolean isVisible() {
	return isVisible;
	}
	}

view raw Heptagon.java hosted with ❤ by GitHub

It ought to look at least something like this: