private Resource() throws IOException {
        // Initialize all needed resource
        mTankImages = new BufferedImage[Rule.NUM_OF_TANK_TYPES];
        for (int i = 0; i != Rule.NUM_OF_TANK_TYPES; ++i)
            mTankImages[i] = ImageIO.read(new File("res/tank_" + i + ".png"));
        mGunImages = new BufferedImage[Rule.NUM_OF_GUN_TYPES];
        for (int i = 0; i != Rule.NUM_OF_GUN_TYPES; ++ i)
            mGunImages[i] = ImageIO.read(new File("res/gun_" + i + ".png"));
        mEffectImages = new BufferedImage[Rule.NUM_OF_EFFECT_TYPES];
        for (int i = 0; i != Rule.NUM_OF_EFFECT_TYPES; ++ i)
            mEffectImages[i] = ImageIO.read(new File("res/effect_" + i + ".png"));
        mBulletImages = new BufferedImage[Rule.NUM_OF_BULLET_TYPES];
        for (int i = 0; i != Rule.NUM_OF_BULLET_TYPES; ++i)
            mBulletImages[i] = ImageIO.read(new File("res/bullet_" + i + ".png"));
    }