code: public final boolean release(int arg) {
          if (tryRelease(arg)) {
              Node h = head;
              if (h != null && h.waitStatus != 0)
                  unparkSuccessor(h);
              return true;
          }
          return false;
      }
docs: Releases in exclusive mode.  Implemented by unblocking one or
  more threads if {@link #tryRelease} returns true.
  This method can be used to implement method {@link Lock#unlock}.
  
  @param arg the release argument.  This value is conveyed to
  {@link #tryRelease} but is otherwise uninterpreted and
  can represent anything you like.
  @return the value returned from {@link #tryRelease}