I am getting a "the function display () does not exist" for my quiltpatterns tiles even though there is a display function in that subclass. What am I not getting?



PFont fontInstructions; // create a variable to load the font

PImage [] quiltPatterns = new PImage [4]; // declare a variable that stores an array of quilting patterns images from clip art

EmptyGrid myEmptyGrid;


void setup() {  // call the setup function to define initial enviroment properties

  size(900, 700);  // set the canvas size at 800 pixels by 800 pixels
  background(230); // set background color to light gray

  fontInstructions=loadFont("CurlzMT-48.vlw");  // load the font used for the text in a data file attached to this file
  textFont (fontInstructions);  // set the loaded font as the current one to use

  for (int q = 0; q < quiltPatterns.length; q++) {  // create an array that loads the array of quilt patterns as numbered files
    quiltPatterns[q] = loadImage("pattern" + (q+1) + ".gif");  // load each quilt pattern individually based on its numbered file
  }  // end the for loop for loading the array of quilt patterns as numbered files

  myEmptyGrid= new EmptyGrid (color(227, 208, 140), 100);
}  // end the setup function

void draw () {  // call the draw function

  background(230); // reset background color to light gray everytime the draw function is recalled

  for (int q = 0; q < quiltPatterns.length; q++) {  // create an array that loads the array of quilt patterns as numbered files
    quiltPatterns[q].display();
  }  // end the for loop for loading the array of quilt patterns as numbered files


  myEmptyGrid.display();
 
}  // end the draw function



abstract class Grid {


  float sizeOfSquares;
  color gridClr;


  Grid(color tempgridClr, float tempsizeOfSquares) {

    gridClr=tempgridClr;
    sizeOfSquares=tempsizeOfSquares;
  }  // end of the constructor



  void display () {

    // initialization of quilt patterns (from Shiffman page 261)

    for (int i=0;i<width;i+=sizeOfSquares) {
      for (int j=0;j<height;j+=sizeOfSquares) {
        fill(gridClr);
        rect(i, j, sizeOfSquares, sizeOfSquares);
      }
    }
  }  // end of the display function
}


class EmptyGrid extends Grid {


  EmptyGrid(color tempgridClr, float tempsizeOfSquares) {
   
super (tempgridClr, tempsizeOfSquares);
       
    gridClr=tempgridClr;
    sizeOfSquares=tempsizeOfSquares;
   
  }  // end of the constructor

 
   void display () {

    // initialization of quilt patterns (from Shiffman page 261)

    for (int i=200;i<width;i+=sizeOfSquares) {
      for (int j=100;j<height;j+=sizeOfSquares) {
        fill(gridClr);
        rect(i, j, sizeOfSquares, sizeOfSquares);
      }
    }
  }  // end of the display function 
}  // end of the Grid class


class Patterns extends Grid {


  EmptyGrid(color tempgridClr, float tempsizeOfSquares) {

    super (tempgridClr, tempsizeOfSquares);

    gridClr=tempgridClr;
    sizeOfSquares=tempsizeOfSquares;
  }  // end of the constructor

  void display() {

    image (quiltPatterns[0], 0, height-600, sizeOfSquares, sizeOfSquares);
    image (quiltPatterns[1], 0, height-450, sizeOfSquares, sizeOfSquares);
    image (quiltPatterns[2], 0, height-300, sizeOfSquares, sizeOfSquares);
    image (quiltPatterns[3], 0, height-150, sizeOfSquares, sizeOfSquares);
  }
}


// code for the instructions class

class Instructions {       // create a class for the instructions

 // fields

String instruction1; // create a variable for the first line of the instructions that will appear on the screen
String instruction2; // create a variable for the second line of the instructions that will appear on the screen
String instruction3; // create a variable for the third line of the instructions that will appear on the screen
String instruction4; // create a variable for the fourth line of the instructions that will appear on the screen
String instruction5; // create a variable for the fifth line of the instructions that will appear on the screen

int textX; // create a variable for the X position of the text
int textY; // create a variable for the Y position of the text

}  // end the intructions class