如何在Java中将实体转换为对象

Question

I define a general List which can add any type elements, define as: List<List<Object>> rows = new ArrayList<>() ; but when I get a list from my service layer, the compile process would throw a incompatible types exception, codes sample as below:

List<List<Object>> rows = new ArrayList<>();
List<ProductEntity> result = searchResponse.getProducts();
rows.add(result);

the exception is: incompatible types: java.util.List<com.shopee.data.webapispec.brandseller.entity.product.ProductEntity> cannot be converted to java.util.List<java.lang.Object> when I run the command " mvn clean install ", anyone knows how to handle it?

Answer 1

ProductEntity is a sub class of Object . However List<ProductEntity> is not a subclass of List<Object> .

You need to have List<List<? extends Object>> rows = new ArrayList<>(); List<List<? extends Object>> rows = new ArrayList<>(); to make this work.

See here for details on Generics and Object Hierarchies