java 难题

Given:

class Bird {
  { System.out.print("bl "); }
  public Bird() { System.out.print("b2 "); }
}
class Raptor extends Bird {
  static { System.out.print("r1 "); }
  public Raptor() { System.out.print("r2 "); }
  { System.out.print("r3 "); }
  static { System.out.print("r4 "); }
}
class Hawk extends Raptor {
  public static void main(String[] args) {
    System.out.print("pre ");
    new Hawk();
    System.out.println("hawk ");
  }
}

What is the result?

pre b1 b2 r3 r2 hawk

pre b2 b1 r2 r3 hawk

pre b2 b1 r2 r3 hawk r1 r4

r1 r4 pre b1 b2 r3 r2 hawk

r1 r4 pre b2 b1 r2 r3 hawk

pre r1 r4 b1 b2 r3 r2 hawk

pre r1 r4 b2 b1 r2 r3 hawk

The order of output cannot be predicted.

Compilation fails.

answer is : r1 r4 pre bl b2 r3 r2 hawk


public class InheritTest {

    private InheritTest inherit;

    @Before
    public void init() {
        inherit = new InheritTest();
    }

    public void sayInherit(Raptor obj) {
        System.out.println("obj is raptor");
    }

    public void sayInherit(Bird obj) {
        System.out.println("obj is Bird");
    }
    @Test
    public void inherit() {
        Raptor raptor = new Raptor();
        Hawk hawk = new Hawk();
        inherit.sayInherit(raptor);
        inherit.sayInherit(hawk);

    }
}

what will print out?

answer is :
obj is raptor
obj is raptor