code: public void close() {
          logger.debug("enter - close()");
          try {
              connection = null;
              data = null;        
              synchronized( executions ) {
                  executions.add(this);
                  executions.notifyAll();
              }
          }
          finally {
              logger.debug("exit - close()");
          }
      }
docs: Closes out the event and returns it to the shared stack.