[英]Passing ArrayList<Subclass> to method declared with List<Superclass>
I have a method with a parameter containing generics. 我有一个方法,其中包含一个包含泛型的参数。
public static void readList(List<ModelObject> list)
{
// more code
}
I want to pass an ArrayList
of ModelObjectImplementation
s to this method. 我想将
ModelObjectImplementation
的ArrayList
传递给此方法。
ArrayList<ModelObjectImplementation> myList;
myList = ...
readList(myList); // gives compilation error
ModelObject
is an interface that ModelObjectImplementation
implements. ModelObject
是ModelObjectImplementation
实现的接口。 How can I change the method declaration to allow this? 如何更改方法声明以允许此操作?
You can use wildcards, if you're using Java version 1.5 and higher. 如果您使用的是Java 1.5及更高版本,则可以使用通配符。
public static void readList(List<? extends ModelObject> list)
This solution is more generic, because it fits for all java.util.List
interface implementations and subclasses/subinterfaces of ModelObject
. 此解决方案更通用,因为它适用于
ModelObject
所有java.util.List
接口实现和子类/子接口。 For more details go to wildcards tutorial 有关更多详细信息,请转到通配符教程
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