Bullet Tower Upgrade

// Import for ArrayList and to draw images
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.util.ArrayList;

/**
 * Class for data and methods of the bullet object
 * 
 * @author Sina, Elliott and Christian
 * @version June 16, 2014
 */

public class Bullet
{
	// Declare all the necessary variables for the bullet object
	protected double xPos;
	protected double yPos;
	private double direction;
	protected double size;
	protected int speed;
	protected int damage;
	private final int normalSpeed = 15;
	private final int fastSpeed = 60;
	protected boolean intact;
	private Alien alien;
	protected Tower tower;


	/**
	 * Constructs a bullet object
	 * 
	 * @param xPos the initial x-coordinate of the bullet (same as tower that
	 *            made it)
	 * @param yPos the initial y-coordinate of the bullet (same as tower that
	 *            made it)
	 * @param size the radius of the bullet
	 * @param speed the speed of the bullet (amount it moves per time event)
	 * @param damage the damage the bullet does if it collides with an alien
	 * @param alien the alien the bullet is currently targeted at
	 * @param fast boolean that determines whether this bullet is in fastforward
	 *            or not
	 * @param tower the tower that created this bullet
	 */
	public Bullet(double xPos, double yPos, int size, int speed, int damage,
			Alien alien, Tower tower)

	{
		// Initialize all the bullet variables
		this.xPos = xPos;
		this.yPos = yPos;
		this.size = size;
		this.speed = speed;
		this.damage = damage;
		this.alien = alien;
		this.intact = true;
		this.tower = tower;
		// Adjust the direction of the bullet in the beginning to face the enemy
		this.directionAdjust();

	}

	/**
	 * Adjusts the direction of the bullet in order to face the alien that it is
	 * targeting
	 */
	public void directionAdjust()
	{

		// If the alien is alive the angle that the bullet must face is found
		// using the inverse tangent
		if (alien.isAlive() && alien.onScreen())
		{
			direction = Math.atan((this.yPos - alien.yPos())
					/ (this.xPos - alien.xPos()));
			// Adjust the direction for special cases in inverse tangent (since
			// the range is limited to (-pi/2,pi/2))
			if (this.xPos > alien.xPos())
			{
				direction += Math.PI;

			}
			else if (this.xPos == alien.xPos())
			{
				if (this.yPos > alien.yPos())
					direction = 3 * Math.PI / 2;
				else if (this.yPos < alien.yPos())
					direction = Math.PI / 2;
			}
		}

	}

	/**
	 * Speeds up the bullet to its fast forward speed (4x)
	 */
	public void fastForward()
	{

		this.speed = fastSpeed;
	
	}

	/**
	 * Slows down the bullet to its normal speed
	 */
	public void normal()
	{

		this.speed = normalSpeed;
	

	}

	/**
	 * Changes the bullet's coordinates according to its speed and direction
	 */
	public void move()
	{
		// Adjust the direction and use trigonometry to determine how much x and
		// y should change by
		this.directionAdjust();

		this.xPos += speed * Math.cos(direction);
		this.yPos += speed * Math.sin(direction);

	}

	/**
	 * Draws the bullet
	 * 
	 * @param g Graphics for drawing the bullet
	 */
	public void draw(Graphics g)
	{
		// Used for drawing round shapes to prevent jagged edges
		Graphics2D g2 = (Graphics2D) g;
		g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
				RenderingHints.VALUE_ANTIALIAS_ON);
		// Draws a red circle based on size and coordinates
		g2.setColor(Color.RED);
		g2.fillOval((int) (xPos - size / 2), (int) (yPos - size / 2),
				(int) size, (int) size);

	}

	/**
	 * Checks if the bullet has collided with any of the aliens and if so it
	 * does damage to it or if the bullet has collided with walls
	 * 
	 * @param aliens the ArrayList containing all the aliens currently in the
	 *            game
	 */
	public void collisionCheck(ArrayList<Alien> aliens)
	{
		// For each alien, check if the alien is in the appropriate collision
		// range and if so
		// do damage to the alien, increase the hits for the tower and change
		// the status of the bullet
		// to not intact
		for (Alien nextAlien : aliens)
		{
			if ((this.xPos - nextAlien.xPos()) * (this.xPos - nextAlien.xPos())
					+ (this.yPos - nextAlien.yPos())
					* (this.yPos - nextAlien.yPos()) <= (this.size / 2.0 + 27
					/ Math.sqrt(2) + this.speed / 2)
					* (this.size / 2.0 + 27 / Math.sqrt(2) + this.speed / 2)
					&& nextAlien.isAlive())
			{
				nextAlien.takeDamage(this.damage);
				tower.increaseNoOfHits();
				this.intact = false;

			}
		}
		// Checks if the bullet is off of the board and if so the bullet is no
		// longer intact
		if (this.xPos < 0 || this.yPos < 0 || this.xPos > 729
				|| this.yPos > 675)
		{
			this.intact = false;

		}

	}

	/**
	 * Method determines if a bullet is still intact or not
	 * 
	 * @return boolean for whether or not the bullet is intact or not
	 */
	public boolean isIntact()
	{
		return this.intact;
	}

}