Graphics Plotter

Demonstration

The graphics plotter allows users to plot shapes on a canvas. The current commands are:

circle x y r // plots a circle of radius r with center @ (x, y)
square x y s // plots a square with side = s and
// upper left corner @ (x, y)
triangle x y a // plots a triangle with altitude a and
// upper left corner @ (x, y)

In the future we want to add more types of shapes.

For example, here's a typical control loop session:

Here's the corresponding graphics window:

The Viewer

Here's the standard viewer. You should know the imports needed:

public class FrameViewer {

public static final int FRAME_WIDTH = 300;
public static final int FRAME_HEIGHT = 400;

public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setSize(FRAME_WIDTH, FRAME_HEIGHT);
frame.setTitle("Plot Viewer");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
PlotComponent plotter = new PlotComponent();
frame.add(plotter);
frame.setVisible(true);
plotter.controlLoop();
}
}

Some Shapes

Here is a library of existing shapes. Unfortunately, the names of the drawing methods differ. You may add to these declarations, but you may not modify any of the existing code.

Circles

class Circle {
private int xc, yc, radius;

public Circle(int x, int y, int r) {
xc = x;
yc = y;
radius = r;
}

public void draw(Graphics2D gc) {
Ellipse2D.Double c = new Ellipse2D.Double(
xc – radius/2, yc – radius/2, radius, radius);
gc.draw(c);
}
}

Squares

class Square {
private int xc, yc, side;

public Square(int x, int y, int s) {
xc = x;
yc = y;
side = s;
}

public void paint(Graphics2D gc) {
Rectangle2D.Double c = new Rectangle2D.Double(
xc, yc, side, side);
gc.draw(c);
}
}

Triangles

class Triangle {
private int xc, yc, length;

public Triangle(int x, int y, int l) {
xc = x;
yc = y;
length = l;
}

public void display(Graphics2D gc) {
Line2D.Double side1 = new Line2D.Double(
xc + length /2, yc, xc, yc + length);
Line2D.Double side2 = new Line2D.Double(
xc + length /2, yc, xc + length, yc + length);
Line2D.Double side3 = new Line2D.Double(
xc, yc + length, xc + length, yc + length);

gc.draw(side1);
gc.draw(side2);
gc.draw(side3);
}
}

The Plotter

Here's the problem: the plotter component uses an array list that holds the forms to be plotted. But this array list is heterogeneous. It contains many types of forms: circles, squares, triangles, etc. So you must define an appropriate Form interface and retool the shapes so that they implement this interface.

class PlotComponent extends JComponent {
private ArrayList<???> forms = new ArrayList<???>();

public void paintComponent(Graphics gc) {
Graphics2D gc2d = (Graphics2D)gc;
for(int i = 0; i < forms.size(); i++) {
forms.get(i).plot(gc2d);
}
}

public void controlLoop() {
Scanner kbd = new Scanner(System.in);
while(true) {
System.out.print("-> ");
String token = kbd.next();
if (token.equals("quit")) {
break;
} else if (token.equals("circle")) {
int xc = kbd.nextInt();
int yc = kbd.nextInt();
int radius = kbd.nextInt();
Circle x = new Circle(xc, yc, radius);
forms.add(x);
repaint();
System.out.println("done");
} else if (token.equals("square")) {
int xc = kbd.nextInt();
int yc = kbd.nextInt();
int side = kbd.nextInt();
Square x = new Square(xc, yc, side);
forms.add(x);
repaint();
System.out.println("done");
} else if (token.equals("triangle")) {
int xc = kbd.nextInt();
int yc = kbd.nextInt();
int alt = kbd.nextInt();
Triangle x = new Triangle(xc, yc, alt);
forms.add(x);
repaint();
System.out.println("done");
} else {
System.err.println("Unrecognized command: " + token);
}
}
System.out.println("bye");
System.exit(0);
}
}