Getting started with the j2_2d games (4) join the bullet group to implement collision calculation

Bullets are essential in aircraft games. They are numerous and full of the whole screen. These random or small objects with a certain amount of AI are not always easy to implement, sometimes you have to consider many performance-related issues. We have previously defined a GameObject to facilitate the reuse of Sprite. because we have a lot of bullets, it is impossible to share the same Sprite without adding one bullet. We implement this by inheriting GameObject.
The following describes the bullet categories:
It will inherit from GameObject;
Record the number of bullets;
A bullet status Array records the type, position x, y, speed vx, vy, and alive of each bullet.
Initialize bullets
Draw a bullet to the screen.
A collision detection method.
Well, let's take a look. The following is the definition of the bullet class. Pay attention to this idea-reuse Sprite, which is very important. (Many designs of tony are referenced here)
Public class Bullets extends GameObject {
Private int [] [] bullets; // array of bullet states
Private int bulletstotal; // The length of the array
Private Random rnd; // Random Number
Public static final int BULLET_TYPE_LEFT = 0; // Position Type of the bullet Initialization
Public static final int BULLET_TYPE_RIGHT = 1; // It can be divided into four types: upper, lower, and left.
Public static final int BULLET_TYPE_TOP = 2;
Public static final int BULLET_TYPE_BOTTOM = 3;
Private int width, height; // the height and width of the screen, used for random bullet positions
Public Bullets (Image img, int picwidth, int picheight, int bulletstotal, int width, int height ){
Super (img, picwidth, picheight );
This. bulletstotal = bulletstotal;
Bullets = new int [bulletstotal] [6];
Rnd = new Random ();
This. width = width;
This. height = height;
}
Public void initBullets () {// array of initial bullet status
For (int I = 0; I <bullets. length; I ++ ){
InitBullet (I );
}
}
Private void initBullet (int I) {// initialize the index bullet
Bullets [I] [0] = (rnd. nextInt () & 0x7fffffff) % 4; // type
Bullets [I] [5] = 1; // alive 1 indicates survival, 0 indicates death
Switch (bullets [I] [0]) {
Case BULLET_TYPE_LEFT:
Bullets [I] [1] =-5;
Bullets [I] [2] = (rnd. nextInt () & 0x7fffffff) % height;