Why does the validation not satisfy? I can't find my error.

"In the SpaceInvadersGame class's removeDeadBullets() method, you need to remove all projectiles from the playerBullets list if the projectile is "dead" OR the sum of the y coordinate and the projectile's height field is less than zero." private void removeDeadBullets() { ListIterator<Bullet> it = enemyBullets.listIterator(); while (it.hasNext()) { Bullet bullet = it.next(); if ((!bullet.isAlive) || (bullet.y >= (HEIGHT -1)) || ((bullet.height + bullet.y) < 0)) { it.remove(); } } }