Error on synchronization on objects in Java

This example fails with `unexpected statement: monitorenter`

```
public class monitorenter1
{
  public boolean doIt(boolean b)
  {
    boolean a;
    synchronized(this) {
      a = !b;
    }
    return a;
  }
  public void test()
  {
    assert(doIt(false));
  }
}
```

the critical section is enclosed between `monitorenter` and `monitorexit` in the bytecode.
