Particle Engine

public class ParticleEngine implements SFEngine{

    // Used by particle emitter control
    int ticks = 0;

    /*
     * A lower number reduces the amount of particles emitted.
     * A higher number increases the amount of particles emitted.
     *
     * Limit cannot exceed 1000, or a 'division by zero' error
     * will be thrown, halting the program.
     */
    final int particleLimit = 500;

    // Values used for setting the backdrop of the game
    public int redHue = 1;
    public int greenHue = 28;
    public int blueHue = 36;

    // Holds all particles
    public static ArrayList<Entity> particles = new ArrayList<Entity>();

    // Particle Kill Queue
    public ArrayList<Entity> toKill = new ArrayList<Entity>();

    @Override
    public void tickEngine() {
        // Ticks the Particle Emitter Control
        if (ticks < 1000) {
            ticks ++;
        } else {
            ticks = 0;
        }

        // Tick Particles
        tickElements();

        // Particle Emitter
        /*
         * The particle emitter works by limiting the number of instantiated particles
         * per 1000 ticks. The number of particles spawned per 1000 ticks is specified
         * by the particleLimit(int).
         */
        if (ticks % (1000 / particleLimit) == 0) {
            spawnParticle();
        }

        // Perform Object Removal
        checkStatus();
        process();
    }

    public void spawnParticle() {
        // Particles can range in size from 1 - 6
        int size = new Random().nextInt(7);

        // If the particle size is set as 0, set it as 1
        if (size < 1) size = 1;

        // X-Position may range from 0 - the frame's current width
        int xPos = new Random().nextInt(INIT.currentWidth - (size - 1));

        // Y-Position is always at -10, which is above the top of the screen.
        // This is so that the user cannot see the particles spawning on screen
        int yPos = -10;

        // Particles can have a speed of descent ranging from 1 - 4
        int ySpeed = new Random().nextInt(5);

        // If the descent speed is set as 0, set it as 1
        if (ySpeed < 1) ySpeed = 1;

        // This is used for the particle's color selector
        int random = new Random().nextInt(5);

        // Instantiate new particle
        particles.add(new Particle(xPos, yPos, ySpeed, size, -1, random));
    }

    @Override
    public void renderEngine(Graphics g) {
        // Set Background Color
        g.setColor(new Color(redHue, greenHue, blueHue));

        // Fill the screen
        g.fillRect(0, 0, INIT.currentWidth, INIT.currentHeight);

        // Render particles
        renderElements(g);
    }

    @Override
    public void tickElements() {
        for (Entity part:particles) {
            part.tick();
        }
    }

    @Override
    public void renderElements(Graphics g) {
        for (Entity part:particles) {
            part.render(g);
        }
    }

    @Override
    public void checkStatus() {
        for (Entity part:particles) {
            if (part.isDead()) {
                toKill.add(part);
            }
        }
    }

    @Override
    public void process() {
        for (Entity part:toKill) {
            particles.remove(part);
        }

        toKill.clear();
    }
}