Java Code:
import java.util.Observable;
import java.util.Observer;

public class SampleCheckInterface {

  public static void main(String[] args) {
    Class observer = Observer.class;
    Class observable = Observable.class;
    verifyInterface(observer);
    verifyInterface(observable);
  }

  static void verifyInterface(Class c) {
    String name = c.getName();
    if (c.isInterface()) {
      System.out.println(name + " is an interface.");
    } else {
      System.out.println(name + " is a class.");
    }
  }
}