Gson TypeToken with dynamic ArrayList item type

Question

I have this code:

Type typeOfObjectsList = new TypeToken>() {}.getType();
List objectsList = new Gson().fromJso         


        

Answer 1

The syntax you are proposing is invalid. The following

new TypeToken>

is invalid because you're trying to pass a method invocation where a type name is expected.

The following

new TypeToken>() 

is not possible because of how generics (type erasure) and reflection works. The whole TypeToken hack works because Class#getGenericSuperclass() does the following

Returns the Type representing the direct superclass of the entity (class, interface, primitive type or void) represented by this Class.

If the superclass is a parameterized type, the Type object returned must accurately reflect the actual type parameters used in the source code.

In other words, if it sees ArrayList, that's the ParameterizedType it will return and you won't be able to extract the compile time value that the type variable T would have had.

Type and ParameterizedType are both interfaces. You can provide an instance of your own implementation.