code: public boolean isClosed()
     {
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.entry(this, tc, "isClosed");
        boolean retValue = false;
  
        if (connectionProxy == null)
        {
           retValue = closed;
        }
        else
        {
           retValue = closed || connectionProxy.isClosed();
        }
  
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(this, tc, "isClosed", ""+retValue);
        return retValue;
     }
docs: This method identifies whether we are able to close this proxy
  object. If this object represents a session object, then this
  can only be closed if we have not been closed and if the connection
  has not been closed. If it represents a connection, then we
  can only close if we have not already been closed.
  
  @return Returns true if we have already been closed or if the
  underlying connection has been closed.