Move the snake

// create a new segment
Snake s = new Snake(); 
// create temporary segment array of equal length
Snake[] oldSnake = new Snake[snakeBody.length];
// copy data from original array to temporary array
for(int i=0; i<snakeBody.length; i++) oldSnake[i] = snakeBody[i];
// re-create original array allowing one more element
snakeBody = new Snake[snakeBody.length+1];
// copy data from temporary array to re-created original array
for(int i=0; i<oldSnake.length; i++) snakeBody[i] = oldSnake[i];
// add the new segment to the array
snakeBody[snakeBody.length-1] = s;
// add the new segment into the world
addObject(snakeBody[s, previousLocationX, previousLocationY);

Snake[] oldSnake = new Snake[snakeBody.length];
System.arraycopy(snakeBody, 0, oldSnake, 0, snakeBody.length);
snakeBody = new Snake[oldSnake.length+1];
System.arraycopy(oldSnake, 0, snakeBody, 0, oldSnake.length);
snakeBody[snakeBody.length-1] = new Snake();
addObject(snakeBody[snakeBody.length-1], previousLocationX, previousLocationY);

    public void checkWalls()
    {
        // check if hit the edge of screen
        if(snakeBody[0].getX()+speedX < 0 || snakeBody[0].getX() + speedX > getWidth())
        {
            die(); return;
        }

        if (snakeBody[0].getY() + speedY  < 0 || snakeBody[0].getY() + speedY > getHeight())
        {
            die();return;
        }
    }

public void checkWalls()
    // check if at edge of screen
    if(snakeBody[0].getX() + speedX < 15 || snakeBody[0].getX() + speedX > getWidth() - 15 ||
       snakeBody[0].getY() + speedY < 15 || snakeBody[0].getY() + speedY > getHeight() - 15) die;
}

public void growSnake()
    {

        //create a new segment
        Snake s = new Snake();
        // create temporary segment array of equal length 
        Snake[] oldSnake = new Snake[snakeBody.length];
        // copy data from original array to temporary array
        for(int i=0; i<snakeBody.length; i++)
        
        {
            oldSnake[i] = snakeBody[i];
        }
        
        // re-create original array allowing one more element
        snakeBody = new Snake[snakeBody.length+1];

        // copy data from temporary array to re-created original array
        for(int i=0; i<oldSnake.length; i++)
        {
            snakeBody[i] = oldSnake[i];
        }
        // add the new segment to the array, in the last spot
        snakeBody[snakeBody.length-1] = s;
        // add the new segment into the world
        addObject( s, previousLocationX, previousLocationY);  

// add the following at the top of the world class
import java.util.List;
import java.util.ArrayList;
// declare your ArrayList instance
private List<Snake>snakeBody= new ArrayList();
// use 'snakeBody.size()' instead of 'snakeBody.length'
// add to the array with
Snake snake = new Snake();
snakeBody.add(snake);
// to get the specific snakeBody element i, use
snakeBody.get(i);