void Displayable.addCommand(Displayable dsp, Command c);
  c   dsp.


Displayable dsp Displayable.fromObject(Object obj);
  obj   dsp    .


boolean shown Displayable.isShown(Displayable dsp);
,    dsp     .


void Displayable.removeCommand(Displayable dsp, Command c);
  c   dsp.


void Displayable.setCommandListener(Displayable dsp, CommandListener coml);
   coml   dsp.   - ,  , ,     .


Object obj Displayable.toObject(Displayable dsp);
  dsp   obj.