Thread: How do I let the tail of my snake grow?

It starts at 2, but when the snake eats an apple it becomes 1 and after it eats another apple, it goes back to 2. Please help!

This is my code:
//x, y
int xHead = 3, yHead = 6;

int xMax = 13, yMax = 13;

int xApple, yApple;

int xRandom = 10, yRandom = 7;

int leftOffset = 700, topOffset = 280;

int dir = 0;

//size
int tileSize = 40;
int appleSize = 30;

//More
ArrayList<Integer> xTail = new ArrayList<Integer>(), yTail = new ArrayList<Integer>();
int score;
int spd;
boolean gameOver = false;
boolean youWon = false;

void setup() {
size(1920, 1080);
frameRate(8);
xTail.add(xHead);
yTail.add(yHead);
xTail.add(xHead);
yTail.add(yHead);
xTail.add(xHead);
yTail.add(yHead);
}

void draw() {
background(170, 150, 220);

Field();

if(dir == 1 && xHead < xMax - 1) {xHead += 1;} //Right
if(dir == 2 && yHead < yMax - 1) {yHead += 1;} //Down
if(dir == 3 && xHead > 0) {xHead -= 1;} //Left
if(dir == 4 && yHead > 0) {yHead -= 1;} //Up

AppleEaten();
Apple();
Score();

for (int i = (xTail.size() - 1); i >= 0; i--) {
if (i == 0) {
xTail.set(i, xHead);
yTail.set(i, yHead);
} else {
xTail.set(i, xTail.get(i-1));
yTail.set(i, yTail.get(i-1));
}

fill(60, 170, 70);
rect(leftOffset + xTail.get(i) * tileSize, topOffset + yTail.get(i) * tileSize, tileSize, tileSize);
fill(60, 170, 70);
rect(leftOffset + xTail.get(i) * tileSize, topOffset + yTail.get(i) * tileSize, tileSize, tileSize);
}
Head();
}
}

void keyPressed(){
if(keyCode == 39 && dir != 3) {dir = 1;}
if(keyCode == 40 && dir != 4) {dir = 2;}
if(keyCode == 37 && dir != 1) {dir = 3;}
if(keyCode == 38 && dir != 2) {dir = 4;}
}

void Field(){
int xWaarde = 0;
int yWaarde = 0;
fill(100, 240, 100);
for(int i = 0; i < xMax; i++){
for(int j = 0; j < yMax; j++){
strokeWeight(0);
if((i+j) % 2 == 0) {fill(100, 230, 100);}
else {fill(100, 240, 100);}
rect(leftOffset + xWaarde * tileSize, topOffset + yWaarde * tileSize, tileSize, tileSize);
yWaarde ++;
}
yWaarde = 0;
xWaarde ++;
}
}

void Head(){
fill(60, 170, 70);
rect(leftOffset + xHead * tileSize, topOffset + yHead * tileSize, tileSize, tileSize);
}

void Apple() {
xApple = leftOffset - (tileSize / 2) + (xRandom * tileSize);
yApple = topOffset - (tileSize / 2) + (yRandom * tileSize);
fill(255, 0, 0);
ellipse(xApple, yApple, appleSize, appleSize);
}

void AppleEaten(){
if(xHead == xRandom - 1 && yHead == yRandom - 1){
score++;
xRandom = round(random(1, 13));
yRandom = round(random(1, 13));
xTail.add(xHead);
yTail.add(yHead);
}
}


void Score(){
fill(0);
text(score, leftOffset, topOffset - 20);
}