Vault Plugin Help

Hey, I've implemented the "Vault" Plugin in my plugin and want to get access to the methods of the economy part, it would be the best if I could use the iConomy methods. I can use the variable economy
"public static Economy economy = null;"
but it always gives me "NullPointerException" if I try to use one of the methods like:
"economy.getName();"

of cause I know I myself set the variable to "null" but I don't know what I have to set the variable to get it work. I have the setup, that goes like this:
"private boolean setupEconomy()
{
RegisteredServiceProvider<Economy> economyProvider = getServer().getServicesManager().getRegistration(net.milkbowl.vault.economy.Economy.class);
if (economyProvider != null) {
economy = economyProvider.getProvider();
}

return (economy != null);
}"

I hope someone can tell me what I have to do to be able to use the methods without getting errors
And what do I have to add to my plugin.yml and how to get vault work?

 

Did you call the setupEconomy() function in your onEnable() ?

 

yes I called it there

 

what kind of errors you're getting? those of NoClassDefFoundError?

 

I downloaded this and on day 2 it says: [SEVERE] [Fatal Error] :3:33: The reference to entity "ssid" must end with the ";" delimiter. I looked through all of the plugins and when I put this plugin on it showed this error, but it was only with this plugin. I searched through everything that came with this plugin but it didn't show up anywhere.