object在执行时不知道它的泛型类型。只需创建一个原始类型的新实例（ java.util.ArrayList ）。目标对象不会知道差异（因为不是任何区别）。

An object doesn't know about its generic type at execution time. Just create a new instance of the raw type (java.util.ArrayList). The target object won't know the difference (because there isn't any difference).

基本上Java泛型是一个编译时的技巧，在编译的类中使用元数据，但只是在执行时进行转换。有关详细信息，请参阅 Java泛型常见问题解答。

Basically Java generics is a compile-time trick, with metadata in the compiled classes but just casting at execution time. See the Java generics FAQ for more information.