如何获取泛型类型的类？

Question

How can I create a Class that represents a generic object?

List<String> list = new List<String>();
Class c1 = list.class;
Class c2 = Class.forName(???); // <- how?
assert c1 == c2;

Answer 1

A class object is not specific to the particular class that is satisfying its type parameter:

assert (new ArrayList<String>()).getClass() == (new ArrayList<Integer>()).getClass();

It's the exact same object regardless of how it's typed.

Answer 2

You can not, since generic information is not present during runtime, due to type erasure .

Your code can be written like:

List<String> list = new ArrayList<String>();
Class c1 = list.getClass();
Class c2 = Class.forName("java.util.ArrayList");
System.out.println(c1 == c2); // true

Answer 3

Class does not represent general types. The appropriate type to use is java.lang.reflect.Type , in particular ParameterizedType . You can get these objects via reflection or make your own.

(Note, generics is a static-typing feature so isn't really appropriate for runtime objects. Static typing information happens to be kept in class files and exposed through the reflection API on reflective objects.)

Answer 4

This worked for me: (Class<List<MYTYPE>>) Class.forName("java.util.ArrayList")

So for your case:

List<String> list = new List<String>();
Class c1 = list.class;
Class c2 = (Class<List<String>>) Class.forName("java.util.ArrayList")
assert c1 == c2;