ScalaSTM waiting example in Java

gistfile1.java

import scala.concurrent.stm.*;
import scala.concurrent.stm.japi.*;

public class a {
  public static void retry() {
    final InTxn txn = Txn.findCurrent(TxnUnknown$.MODULE$).get();
    Txn.retry(txn);
  }

  public static void main(final String[] args) {
    final Ref.View<Integer> x = STM.newRef(0);

    // this thread will change x after 2 seconds
    new Thread() {
      public void run() {
        System.out.println("bg thread sleeping");
        try {
          Thread.sleep(2000);
        } catch (final InterruptedException ex) {
          throw new RuntimeException("unexpected", ex);
        }
        System.out.println("changing x");
        x.set(1);
      }
    }.start();

    STM.atomic(new Runnable() {
      public void run() {
        if (x.get() == 0) {
          // wait until x is non-zero
          retry();
        }
      }
    });

    System.out.println("waiting finished");
  }
}