Is the T class in generic Class<T> assignable from another class?

Question

Edit Since there were many downvotes and people who didn't understand what I'm asking for, I'll rephrase:

How do I find out at runtime what is the class that foo was generified from?

public boolean doesClassImplementList(Class<?> genericClass)
{
  // help me fill this in
  // this method should return true if genericClass implements List
  // I can't do this because it doesn't compile:
  return genericClass instanceof List;
}

Answer 1

you cannot in Java (type erasure)

Answer 2

You should be using Class.forName( "fully_qualified_name" ) to generate a Class object, or using the .getClass() method on an already instantiated object. Also, for int types, the class is defined in the Integer.TYPE property.

I need a little more clarification of what you are attempting to do, match the same type? You can use a number of methods, what is the end goal?

Ok, now that you've clarified... heres some help ... just pass in a class..

public boolean doesClassImplementList(Class genericClass)
{
  // help me fill this in
  // this method should return true if genericClass implements List
  // I can't do this because it doesn't compile:

  //this will give you a a list of class this class implements
  Class[] classesImplementing = genericClass.getInterfaces();

  //loop through this array and test for:
  for(int i=0; i<classesImplementing.length; i++) {
   if (classesImplementing[i].getName().equals("java.util.List")) {
    return true;
   }
  }
  return false;
}

Answer 3

Class<Integer> is a type declaration, you can't assign it to a variable, as you are doing on your first line.

Class<Integer> is basically a way of referencing the Integer type, so you can pass it as a parameter. It does affect some methods (such as cast) but it is basically a way of providing a generic parameter to a method and associate it with a type.

For example:

public <T> T someMethod(Object someObject, Class<T> castTo) {
     return castTo.cast(someObject);
}

Answer 4

Class.isAssignableFrom