processing4/java/examples/Basics/Structure/Functions/applet/Functions.java

import processing.core.*; 

import java.applet.*; 
import java.awt.*; 
import java.awt.image.*; 
import java.awt.event.*; 
import java.io.*; 
import java.net.*; 
import java.text.*; 
import java.util.*; 
import java.util.zip.*; 
import java.util.regex.*; 

public class Functions extends PApplet {

/**
 * Functions. 
 * 
 * The drawTarget() function makes it easy to draw many distinct targets. 
 * Each call to drawTarget() specifies the position, size, and number of 
 * rings for each target. 
 */

public void setup() 
{
  size(200, 200);
  background(51);
  noStroke();
  smooth();
  noLoop();
}

public void draw() 
{
  drawTarget(68, 34, 200, 10);
  drawTarget(152, 16, 100, 3);
  drawTarget(100, 144, 80, 5);
}

public void drawTarget(int xloc, int yloc, int size, int num) 
{
  float grayvalues = 255/num;
  float steps = size/num;
  for(int i=0; i<num; i++) {
    fill(i*grayvalues);
    ellipse(xloc, yloc, size-i*steps, size-i*steps);
  }
}

  static public void main(String args[]) {
    PApplet.main(new String[] { "Functions" });
  }
}