Java如何转换整个列表

Question

这个问题已经有答案了:

How do you cast a List of supertypes to a List of subtypes? (20 个回答)

已关闭 7 年前。

如何在 Java 中转换完整列表而不进行迭代。我有这个功能:

private List<Object> getItems (List<Object> list, Pagination pagination) {

        if (list.size() > pagination.getItemsXPage()) {

            int init = (pagination.getCurrentPage()-1)* pagination.getItemsXPage();
            int end =  init +  pagination.getItemsXPage();

            if (end > list.size()) {
                end = list.size();
            }

            return list.subList(init, end);

        } else {

            return list;                        
        }       

    }

我想这样做，但不可能？

List<ApplicationSearchItem> applicationSearchItem = (List) getItems (list, searchCriteria.getCategoryProductsPagination()); 

Answer 1

在这种情况下，您将使用泛型方法声明:

By now, you will have learned to avoid the beginner's mistake of trying to use Collection< Object > as the type of the collection parameter. You may or may not have recognized that using Collection< ? > isn't going to work either. Recall that you cannot just shove objects into a collection of unknown type.

from oracle generic methods tutorial

返回类型由参数列表的类型定义:

private <T> List<T> getItems (List<T> list, Pagination pagination) {
 ... 
}