Wednesday night puzzle

2010, Dec 08 One min read

What’s the result of running this piece of code?

a) Done. b) InterruptedException is thrown c) It depends d) Code doesn’t compile

import java.util.Vector;

public class Main {
  interface A {
  }

  static class AImpl implements A {
    static AImpl DUMMY = new BImpl();
  }

  interface B extends A {
  }

  static class BImpl extends AImpl implements B {
  }

  public static void main(String[] args) throws InterruptedException {
    final Vector<Object> values = new Vector<Object>();

    Thread thread = new Thread() {
      @Override
      public void run() {
        values.add(AImpl.DUMMY);
      }
    };
    thread.start();
    values.add(new BImpl());
    thread.join();

    System.out.println("Done.");
  }
}