我有一段代碼如下 private Product createProduct(ProductParmas params){   Product product = repository.getProduct(id)   ProductBuilder.Builder builder = new ProductBuilder.Builder(); // this is a                                                             product builder   if(product ==  null){         builder.location("abc").quantity(5).price(10)         if(parmas.getAvaiability() != null){              builder.availability(parmas.getAvaiability())         }   }   // I also want to set Availability on obj product, but there are no setters so I have to create an instance of ProductBuilder, copy values from product and also set availability. Is there a cleaner way to come both if product is null or not null and set availability field?}我還想在 obj 產品上設置可用性，但沒有設置器，所以我必須創建 ProductBuilder 的實例，從產品復制值并設置可用性。如果產品為空或不為空并設置可用性字段，是否有更簡潔的方法來執行此操作？