public void popTrap(Class<? extends Trap> aClass) {
    if (!aClass.isInstance(myTrapStack.getHead())) {
      throw new IllegalStateException("Unexpected trap-stack head (wanted: "+aClass.getSimpleName()+"); stack: "+myTrapStack);
    }
    myTrapStack = myTrapStack.getTail();
  }
public void popTrap(Class<? extends Trap> aClass)