How to get the class of type variable in Java Generics

Question

I\'ve seen similar questions but they didnt help very much.

For instance I\'ve got this Generic Class:

public class ContainerTest
{

    public          


        

Answer 1

No. It is not possible because of type erasure (the type parameters are compiled as Object + type casts). If you really need to know/enforce the type in runtime you may store a reference to a Class object.

public class ContainerTest {
   private final Class klass;
   private final List list = new ArrayList();

   ContainerTest(Class klass) {
     this.klass = klass;
   }

   Class getElementClass() {
     return klass;
   }

   void add(T t) {
      //klass.cast forces a runtime cast operation
      list.add(klass.cast(t));
   }
}

Use:

ContainerTest c = new ContainerTest<>(String.class);