How do i make a block that acts like a mob spawner?

if im wan't to make a "living mob spawner" i'm makeing this code [ i use zombie but it cut be enyting]:

                if (0.8 <= Math.random()) {

                    if (world instanceof ServerLevel _level) {

                        Entity entityToSpawn = new Zombie(EntityType.ZOMBIE, _level);

                        entityToSpawn.moveTo(x, y, z, world.getRandom().nextFloat() * 360F, 0);

                        if (entityToSpawn instanceof Mob _mobToSpawn)

                            _mobToSpawn.finalizeSpawn(_level, world.getCurrentDifficultyAt(entityToSpawn.blockPosition()), MobSpawnType.MOB_SUMMONED,

                                    null, null);

                        world.addFreshEntity(entityToSpawn);

                    }

                }

            }

        }

    }

}

if this is not working, i can make a difrent  code

if you don't undersstent it, i can try to explein it, but it will be dificult