Snake game eating the apples

Processing Coding Questions
1

import processing.core.*;

public class Problem04 extends PApplet {
float scale = height / 18f;
float foodX;
float foodY;
float circleX;
float circleY;
float circleR;
int score = 0;
String scoreTxt = "Score: " + score;

public void settings() {
    fullScreen();

}

public void setup() {
    scale = height / 18f;
    foodX = width / 2f + width / 24f;
    foodY = height / 5.5f;
    circleX = width / 1.4f;
    circleY = height / 2.4f;
    circleR = scale;
    frameRate(5);

}


public void draw() {
    background(0, 0, 0);
    fill(0, 0, 0, 10);
    //snake
    fill(225, 0, 0);
    circle(circleX, circleY, circleR);

    // texts
    fill(0, 225, 0);
    text("Game: Collect Yellow Circles Using Arow Button", width / 2f, height / 12f);
    textSize(20);
    textAlign(CENTER, CENTER);
    text(scoreTxt, width / 2f, height / 1.1f);

    // adding the table
    for (float r = 0; r <= width / 1.4f; r += scale) {

        for (float c = 0; c <= (height / 2f + height / 8f); c += scale) {
            noFill();
            stroke(0, 0, 225);
            rect(r + width / 7f, c + height / 6f, scale, scale);

        }
    }
    // key control
    if (key == CODED) {
        switch (keyCode) {
            case UP:
                circleY -= circleR;
                if (circleY - circleR / 2 <= height / 6f) {
                    circleY = height / 5.1f;
                }
                break;
            case DOWN:
                circleY += circleR;
                if (circleY >= (height / 2f) + (height / 8f)) {
                    circleY = (height / 2f) + (height / 3.3f);
                }
                break;
            case RIGHT:
                circleX += circleR;
                if (circleX - circleR / 2 >= width / 1.4f) {
                    circleX = width / 1.15f - circleR / 2;
                }
                break;
            case LEFT:
                circleX -= circleR;
                if (circleX <= width / 7f) {
                    circleX = width / 6.3f;
                }
                break;
        }
    }
    float gridWidth = (int) (width / 7f) + 21 * scale;
    float gridHeight = (int) (height / 6f) + 12 * scale;
    float x = gridWidth / 2;
    float y = gridHeight / 2;
    fill(255, 255, 0);
    circle(x, y, circleR);

}


public static void main(String[] args) {
    PApplet.main("Problem04");
}

}

Hello, I am trying to code a snake game in processing but I cannot get the snake to eat the apples. also while moving from left to right at the last columns the snake jumps. can someone help me solve these 2 problems?