code: public Set tokens() {
          if (tokenSet == null) {
              tokenSet = new AbstractSetView() {
                  public long size() {
                      return 0;
                  }
  
                  public Iterator iterator() {
                      return new Iterator() {
  
                          public boolean hasNext()
                          {
                              return false;
                          } // hasNext().
  
                          public Object next()
                          {
                              throw new java.util.NoSuchElementException();
                          } // next().
  
                          public boolean hasNext(Transaction transaction)
                                          throws ObjectManagerException
                          {
                              throw new UnsupportedOperationException();
                          } // hasNext().
  
                          public Object next(Transaction transaction)
                                          throws ObjectManagerException
                          {
                              throw new UnsupportedOperationException();
                          } // next().
  
                          public Object remove(Transaction transaction)
                                          throws ObjectManagerException
                          {
                              throw new UnsupportedOperationException();
                          } // remove().
  
                      }; // new Iterator().
                  } // iterator().  
              }; // new AbstractSetView().
          } // if (tokenSet == null). 
          return tokenSet;
      }
docs: /*
  (non-Javadoc)
  
  @see com.ibm.ws.objectManager.ObjectStore#tokens()