code: public void add(
          JInternalFrame internalFrame, Object constraints, int index)
      {
          FrameComponent frameComponent = 
              new FrameComponent(internalFrame, constraints, index);
          frameToComponent.put(internalFrame, frameComponent);
          if (!internalFrame.isIcon())
          {
              container.add(frameComponent, constraints, index);
          }
      }
docs: Add the given internal frame to this layout manager.<br>
  <br>
  Note that this will <b>not</b> add the internal frame to the
  desktop pane that this layout belongs to!
  
  @param internalFrame The internal frame to add
  @param constraints The constraints.
  See {@link Container#add(Component, Object)}
  @param index The index.
  See {@link Container#add(Component, Object, int)}