World/Item from config

How would I go about getting a world or material from a config.yml? Say I have this config.yml with a stringList of banned blocks

Code:

bannedBlocks:
  - TNT
  - Bedrock

I know I would first do something like this

Code:

public [something] getBannedBlocks() {
    for (String item : getConfig().getStringList("bannedBlocks") {
        item.toUpperCase();
        // What now? How do I convert from a string to a Material? Or a string that is a world name to a world object?
    }
    return [list of materials];
}

 

For the world, you can do: World world = Bukkit.getWorld("Worldname");

Edit:

And for the material there is a similar method: Material mat = Material.getMaterial("MaterialName");

 

When you use Material.getMaterial("[Material]"), you have to use the exact material name as presented in the enum. Here is a link for reference: http://jd.bukkit.org/index.html?overview-summary.html