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Wednesday night puzzle

Posted on 2 mins 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.");
  }
}
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