import java.util.BitSet;
import java.util.concurrent.CountDownLatch;
 
public class AnExample {
 
  public static void main(String[] args) throws Exception {
    BitSet bs = new BitSet();
    CountDownLatch latch = new CountDownLatch(1);
    Thread t1 = new Thread(new Runnable() {
      public void run() {
        try {
          latch.await();
          Thread.sleep(1000);
        } catch (Exception ex) {
        }
        bs.set(1);
      }
    });
    Thread t2 = new Thread(new Runnable() {
      public void run() {
        try {
          latch.await();
          Thread.sleep(1000);
        } catch (Exception e) {
        }
        bs.set(2);
      }
    });
 
    t1.start();
    t2.start();
    latch.countDown();
    t1.join();
    t2.join();
   // crucial part here:
    System.out.println(bs.get(1));
    System.out.println(bs.get(2));
  }
}

public class AnExampleTest implements 
      Actor2_Arbiter1_Test<BitSet, BooleanResult2> {
 
 @Override
 public void actor1(BitSet s, BooleanResult2 r) {
  s.set(1);
 }
 
 @Override
 public void actor2(BitSet s, BooleanResult2 r) {
  s.set(2);
 }
 
 @Override
 public void arbiter1(BitSet s, BooleanResult2 r) {
  r.r1 = s.get(1);
  r.r2 = s.get(2);
 }
 
 @Override
 public BitSet newState() {
  return new BitSet();
 }
 
 @Override
 public BooleanResult2 newResult() {
  return new BooleanResult2();
 }
}

 <test name="org.openjdk.jcstress.tests.custom.AnExampleTest">
  <contributed-by>Oleg Shelajev</contributed-by>
  <description>
   Tests if BitSet works well without synchronization.
  </description>
  <case>
   <match>[true, true]</match>
   <expect>ACCEPTABLE</expect>
   <description>
    Seeing all updates intact.
   </description>
  </case>
  <case>
   <match>[true, false]</match>
   <expect>ACCEPTABLE_INTERESTING</expect>
   <description>
    T2 overwrites T1 result.
   </description>
  </case>
  <case>
   <match>[false, true]</match>
   <expect>ACCEPTABLE_INTERESTING</expect>
   <description>
    T1 overwrites T2 result.
   </description>
  </case>
  <unmatched>
   <expect>FORBIDDEN</expect>
   <description>
    All other cases are unexpected.
   </description>
  </unmatched>
 </test>

java -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI -XX:-RestrictContended -jar tests-custom/target/jcstress.jar -t=".*AnExampleTest"

synchronized (bs) {
 bs.set(1);
}