1.12.2 Why does it issue the entire amount at once?

Hi! Tell me pls, why it gives the entire amount at once, although not all items were in the inventory.

Code (Text):

            number = 0;
            ItemStack is = inv.getItem(i);
            /////////////////////////////
            if (is == null || is.getType() == Material.WOOD_SWORD) {
                number += 150;
            } if (is == null || is.getType() == Material.STONE_SWORD){
                number += 175;
            }if (is == null || is.getType() == Material.IRON_SWORD) {
                number += 225;
            } if (is == null || is.getType() == Material.DIAMOND_SWORD) {
                number += 300;
            } if (is == null || is.getType() == Material.GOLD_SWORD) {
                number += 200;
            } if (is == null || is.getType() == Material.DIAMOND_HOE) {
                number += 50;
            }