Draw a Equilateral Polygon according to the number of vertexes in Processing language 2.1

draw_equilateral_polygon.pde

// Size of display
int DISPLAY_WIDTH = 500;
int DISPLAY_HEIGHT = 500;
// Colours
int BLACK = 0;
int WHITE = 255;

int CENTER_X = 0;
int CENTER_Y = 0;
  
EquilateralPolygon polygon;

// This class saves coordinate
class Coordinate {
  int x;
  int y;
  // The Constructor is defined with arguments.
  Coordinate(float _x, float _y) {
    x = int(_x);
    y = int(_y);
  }
  
  public String toString() {
    return x + ", " + y;
  }
}

class EquilateralPolygon {
  int numVertexes;
  int radius;
  float[] angles;
  Coordinate[] vertexes;
  
  EquilateralPolygon(int _numVertexes, int _radius) {
    numVertexes = _numVertexes;
    angles = new float[numVertexes];
    radius = _radius;
  }
  
  public float xVertex(int i, int extra) {
    return cos(angles[i]) * (radius + extra);
  }
  public float yVertex(int i, int extra) {
    return sin(angles[i]) * (radius + extra);
  }
  
  public Coordinate[] vertexes() {
    vertexes = new Coordinate[numVertexes];
    float angleForSingleArc = 2 * PI / numVertexes;
  
    for(int i = 0; i < numVertexes; i++) {
      // Sum up angles
      angles[i] = HALF_PI - angleForSingleArc * i;
      
      float x = xVertex(i, 0);
      float y = - yVertex(i, 0);
      vertexes[i] = new Coordinate(x, y);
    }
    
    return vertexes;
  }
  
  // Put tiny circles onto each vertex
  public void drawVertexes() {
    smooth();
    textAlign(CENTER);
    
    int r = 20;
    for (int i = 0; i < numVertexes; i++) {
      // Draw black circle for the first vertex and draw gray ones for the rest
      int colorValue = i == 0 ? 0 : 200;
      stroke(colorValue);
      strokeWeight(1);
      ellipse(vertexes[i].x, vertexes[i].y, r, r);
    }
  }
  
  public void drawIndexes() {
    for (int i = 0; i < numVertexes; i++) {      
      fill(BLACK);
      text(i, vertexes[i].x, vertexes[i].y);
      noFill();
    }
  }
}
  
void setup() {
  size(DISPLAY_WIDTH, DISPLAY_HEIGHT);
  background(WHITE);
  noLoop(); 
}

void draw() {
  // Displace the drawn polygon by half width and half height of `display`, which means center. 
  // With `translate`, we can calculate coodinate of each vertex as distance from the center of a 
  // diagram, where it's coordinate is as (0, 0), and then, displace the polygon to actual coordinate
  // of `display`.  
  translate(DISPLAY_WIDTH / 2, DISPLAY_HEIGHT / 2);
  
  polygon = new EquilateralPolygon(6, 200);
  polygon.vertexes();
  polygon.drawVertexes();
  polygon.drawIndexes();
  
  saveFrame("result.jpg");
}