Use reflection to create a generic parameterized class in Java

java generics reflection parameterized
luvieere picture luvieere · Jun 16, 2011 · Viewed 8.3k times · Source

How can I use reflection to create a generic parameterized class in Java?

I have 

public class SomeClass<T> {
   public SomeClass<T>() {
   }
}

and I need an instance of it.

I've tried variations of

Class c = Class.forName("SomeClass");

but could not find a syntax that would allow me to get an appropriately typed instance, like, say

SomeType instance = (SomeType)Class.forName("SomeClass<SomeType>").createInstance();

So, how could I go about doing this?

Answer

Chris Jester-Young picture Chris Jester-Young · Jun 16, 2011

Java uses erasure-based generics (i.e., the type parameters are erased at runtime—for example, List<Integer> and List<String> are treated as the same type at runtime). Since reflection is inherently a runtime feature, the type parameters are not used or involved at all.

In other words, you can only instantiate the raw type (SomeClass, not SomeClass<T>) when you're using reflection. You will then have to manually cast the type to the generic version (and generate an unchecked warning).

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