Java中的Cast元素对于每个语句 [英] Cast element in Java For Each statement

问题描述

是否可能（或甚至是明智的）将从for语句中检索的元素强制转换为语句本身中的每个语句？我知道列表中的每个元素将是< SubType> 。

Is it possible (or even advisable) to cast the element retrieved from a for each statement in the statement itself? I do know that each element in list will be of type <SubType>.

IE：

List<BaseType> list = DAO.getList();  
for(<SubType> element : list){ 
    // Cannot convert from element type <BaseType> to <SubType>
    ...
}

而不是：

List <BaseType> list = DAO.getList();
for(<BaseType> el : list){
    <SubType> element = (<SubType>)el;
    ...
}

推荐答案

你真的知道每个条目都是一个子类型吗？ DAO只需要满足 List< BaseType> 契约，如果你假设一个子类，那么我认为某处出错了。我可能更专注于获得DAO的接口正确，并有合同返回你想要的。

Do you really know that each entry is going to be a subtype ? The DAO simply has to fulfill the List<BaseType> contract, and if you're assuming a subclass, then I think something is wrong somewhere. I'd perhaps concentrate more on getting the interface to the DAO correct, and have it contractually return what you want.

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