class Base {}
class Derv extends Base {
  void doIt( Base b) {
    System.out.println("Intro with object of class="+b.getClass().getName()+", hash="+b.hashCode());
    Derv y = (Derv)b; // прокатит на компиляции, но вывалится в рантайме
  }
}
class CastTesting {
  public static void main(String[] a) { new Derv().doIt( new Base() ); }
}

D:\JAVA\>java CastTesting
Intro with object of class=Base, hash=11077203
Exception in thread "main" java.lang.ClassCastException: Base cannot be cast to Derv
        at Derv.doIt(CastTesting.java:5)
        at CastTesting.main(CastTesting.java:9)

class Base {}
class Derv extends Base {}
class CastTesting {
  public static void main(String[] a) {
    Derv y = (Derv)new Base(); // это уже не формальный параметр, тут сразу вроде бы всё определяется
  }
}

interface Flyable { public void fly(); }
class Animal {}
class Bird { // no "extends", no "implements" here!
  public static void main(String[] args) {
    // -!- Animal b1 = (Animal) new Bird();  // inconvertible types
    // -!- Flyable b2 = new Bird(); // incompatible types
    // compiles OK but ClassCastException in runtime.
    // Why does it COMPILES ??
    Flyable b3 = (Flyable) new Bird(); 
  }
}

class Test {
  // case-1:
  static interface Rollable { public void Roll(); }
  static class Tank{ }
  static class Ship{ }
  //..................
  // case-2:
  static class Animal {}
  static class Bird extends Animal {}
  static class Fish extends Animal{}
  public static void main(String[] args) {

    // test-1: compiles OK, CCE in runtime:
    Ship v = (Ship) (Rollable) new Tank();

    // test-2: compiles OK, CCE in runtime:
    Fish f = (Fish) (Animal) new Bird();
  }
}