Szansa na drop ze stona

Witam.

Chciałbym mieć drop ze Stona w którym jest szansa na wydropienie itemów róznych. Narazie mam taki kod ale mi działać nie chce.

    @EventHandler
    public void blockBreakEvent(BlockBreakEvent e) {
        Block b = e.getBlock ( );
        Player p = e.getPlayer ( );


        if (b.getType ( ) == Material.STONE) {

            Random rand = ThreadLocalRandom.current ( );
            double num = rand.nextDouble (  );


            if (num >= 50) {
                p.getInventory ( ).addItem ( new ItemStack ( Material.COAL, 1 ) );
            } else if (num >= 5.4) {
                p.getInventory ( ).addItem ( new ItemStack ( Material.IRON_INGOT, 1 ) );
            } else if (num >= 4.7) {
                p.getInventory ( ).addItem ( new ItemStack ( Material.GOLD_INGOT, 1 ) );
            } else if (num >= 2.7) {
                p.getInventory ( ).addItem ( new ItemStack ( Material.DIAMOND, 1 ) );
            } else if (num >= 2.5) {
                p.getInventory ( ).addItem ( new ItemStack ( Material.EMERALD, 1 ) );
            } else if (num >= 1.8) {
                p.getInventory ( ).addItem ( new ItemStack ( Material.LAPIS_LAZULI, 1 ) );
            }
        }
    }
}