code: protected final void begin() {
          blockedOn(interruptor);
          Thread me = Thread.currentThread();
          if (me.isInterrupted())
              interruptor.interrupt(me);
      }
docs: Marks the beginning of an I/O operation that might block indefinitely.
  
  <p> This method should be invoked in tandem with the {@link #end end}
  method, using a <tt>try</tt>&nbsp;...&nbsp;<tt>finally</tt> block as
  shown <a href="#be">above</a>, in order to implement asynchronous
  closing and interruption for this channel.  </p>