Method addInformation

src/main/java/net/minecraft/item/ItemMap.java:289–305

allows items to add custom lines of information to the mouseover description @param tooltip All lines to display in the Item's tooltip. This is a List of Strings. @param advanced Whether the setting "Advanced tooltips" is enabled

(ItemStack stack, EntityPlayer playerIn, List<String> tooltip, boolean advanced)

     * @param advanced Whether the setting "Advanced tooltips" is enabled
     */
    public void addInformation(ItemStack stack, EntityPlayer playerIn, List<String> tooltip, boolean advanced)
    {
        MapData mapdata = this.getMapData(stack, playerIn.worldObj);

        if (advanced)
        {
            if (mapdata == null)
            {
                tooltip.add("Unknown map");
            }
            else
            {
                tooltip.add("Scaling at 1:" + (1 << mapdata.scale));
                tooltip.add("(Level " + mapdata.scale + "/" + 4 + ")");
            }
        }
    }
}