java - 在java中将泛型类型作为参数传递？

Question

是否可以将类型保存在变量中，
以便实例化这种类型的列表？

//something like that
Type type = Boolean;
List<type> list = new List<type>();
list.add(true);

Answer 1

For the first requirement, you are looking for Class:

Class type = Boolean.class;

However, I don't think the seconds requirement is feasible, since generic types only exist at compile time:

List<type> list = new List<type>(); // invalid code

You can, however, work with List<Object>. It will accept Boolean objects. Whether this will buy you anything untlimately depends on your use case.

Answer 2

Generic is a compile time feature, not run time, so you cannot use variable to determine the generic type, even using NPE's note (using Class) will not compile:

Class<?> type = Boolean.class;
// can't do that...
List<type> list = new List<type>();
list.add(true);

Answer 3

在第二种情况下，当类型未知时，为什么要使用泛型？您可以更好地使用非泛型数组列表（在 jdk 5 之前使用）。

   List a = new ArrayList();
   a.add(object);

更高版本仍然支持这种样式，甚至泛型样式在编译后也会转换为这种形式。您将在上面的代码中收到可以禁止的警告。