jbum, thanks for your help!  However, as I run your code, only the "Fur" runs:



The Furs behave according to the methods display(), jitter(), and scatter() though.  However, my intention was to have the colorful "GumBalls" each containing its own Fur object which move accordingly to its parent GumBall:



I used the following code to achieve the above visual, but the Furs did not move anywhere.  They just stayed frozen while the GumBalls moved around according to the mouse actions:

GumBall[] balls = new GumBall[100];
Fur[] furs = new Fur[100];

void setup() {
  size(480, 480);
  smooth();
  colorMode(RGB);
  randomSeed(2);
  for (int i = 0; i < balls.length; i++) {
    float x = random(width);
    float y = random(height);
    float d = random(10, width/3);
    color c = color(random(0, 255), random(40, 255), random(70, 255), random(30, 100));
    balls[i] = new GumBall(x, y, d, c);
    furs[i] = new Fur(x, y, d, c);
  }
}

void draw() {
  background(255);
  for (int i = 0; i < balls.length; i++) {
    balls[i].display();
    balls[i].jitter();
    balls[i].scatter();
    furs[i].display();
  }
}

// GumBall Class Block (aka the cookie cutter)

class GumBall {
 
  float x;                              
  float y;
  float d;
  float homeX;
  float homeY;
  color c;
  float linger = 0.4;
  float speed = 3;
//  Fur furs = new Fur(x, y, d, c);
  
 
  GumBall(float xi, float yi, float di, color ci) { 
    x = homeX = xi;
    y = homeY = yi;
    d = di;
    c = ci;
//    furs.start();
  }
 
  void display() {    
    noStroke();
    fill(c);
    ellipseMode(CENTER);
    ellipse(x, y, d, d);
    fill(alpha(c));
    ellipse(x, y, d/75, d/75);
  }
 
  void jitter() {
    if ((mouseX < x+100) && (mouseX > x-100)) {
      if ((mouseY < y+100) && (mouseY > y-100)) {
        x += (noise(-speed, speed))*3;
        y += (noise(-speed, speed))*3;
      }
    }
    else {
      x += random(-linger, linger);
      y += random(-linger, linger);
    }
  }
 
  void scatter() {
    float easing = 0.05;
    float targetX = x;
    float targetY = y;
    if (mousePressed) {
      x += (targetX - (random(-d, width+d))) * easing;
      y += (targetY - (random(-d, height+d))) * easing;
    }
    else {
      float easingBack = 0.08;
      x += (homeX - x) * easingBack;
      y += (homeY - y) * easingBack;
    }
  }
}

class Fur extends GumBall {
  
  // Constructor for Fur class inheriting variables from GumBall superclass
  Fur(float x, float y, float d, color c) {
    super(x, y, d, c);
  }
 
  void display() {
      strokeWeight(0);
      stroke(alpha(c));
      pushMatrix();
      translate(x, y);
      for (int deg = 0; deg < 360; deg += 10) {
        line(0, 0, cos(radians(deg)) * (d/2), sin(radians(deg)) * (d/2));
      }
      popMatrix();
  }
}
 

// Of course, the GumBall objects and Fur objects are run separately, resulting in isolated functions.  Is there any way to do it better?