public static UIComponent findParentNamingContainer(UIComponent component,
    boolean returnRootIfNotFound) 
{
        UIComponent parent = component.getParent();
        if (returnRootIfNotFound && parent == null)
        {
            return component;
        }
        while (parent != null)
        {
            if (parent instanceof NamingContainer) return parent;
            if (returnRootIfNotFound)
            {
                UIComponent nextParent = parent.getParent();
                if (nextParent == null)
                {
                    return parent;  //Root
                }
                parent = nextParent;
            }
            else
            {
                parent = parent.getParent();
            }
        }
        return null;
}

Locates the NamingContainer associated with the givem UIComponent .

 public static String getClientId(UIComponent component,
    Renderer renderer,
    FacesContext context) 
{
        //forceId enabled?
        boolean forceId = RendererUtils.getBooleanValue(JSFAttr.FORCE_ID_ATTR,
                component.getAttributes().get(JSFAttr.FORCE_ID_ATTR),false);
        if (forceId && component.getId() != null)
        {
            String clientId = component.getId();
            /**
             * See if there is a parent naming container.  If there is ...
             */
            UIComponent parentContainer = HtmlComponentUtils.findParentNamingContainer(component, false);
            if (parentContainer != null)
            {
                if (parentContainer instanceof UIData)
                {
                    // see if the originally supplied id should be used
                    boolean forceIdIndex = RendererUtils.getBooleanValue(JSFAttr.FORCE_ID_ATTR,
                            component.getAttributes().get(JSFAttr.FORCE_ID_INDEX_ATTR),true);
                    // note: user may have specifically requested that we do not add the special forceId [index] suffix
                    if (forceIdIndex)
                    {
                        int rowIndex = ( (UIData) parentContainer).getRowIndex();
                        if (rowIndex != -1) {
                            clientId = clientId + "[" + rowIndex + "]";
                        }
                    }
                }
            }
            // JSF spec requires that renderer get a chance to convert the id
            if (renderer != null)
            {
                clientId = renderer.convertClientId(context, clientId);
            }
            return clientId;
        }
        else
        {
            return null;
        }
}

Gets the client id associated with the component. Checks the forceId attribute of the component (if present) and uses the orginally supplied id value if that attribute is true. Also performs the required call to convertClientId on the Renderer argument.