Java - remove last known item from ArrayList

OK, so here is my ArrayList:

private List<ClientThread> clients = new ArrayList<ClientThread>();

and here is what I am trying to do:
I am trying to remove the last known item from the ArrayList I posted above. I'm trying to do this with the code below:

    } catch(SocketException re) {


                            String hey = clients.get(clients.size());
                            ClientThread.remove(hey);
                            System.out.println(hey + " has logged out.");
                            System.out.println("CONNECTED PLAYERS: " + clients.size());
}

but I am getting this error:

C:\wamp\www\mystikrpg\Server.java:147: incompatible types
found   : Server.ClientThread
required: java.lang.String
                        String hey = clients.get(clients.size());
                                                ^
C:\wamp\www\mystikrpg\Server.java:148: cannot find symbol
symbol  : method remove(java.lang.String)
location: class Server.ClientThread
                        ClientThread.remove(hey);
                                    ^
2 errors

What am I doing wrong? It's supposed to remove the last known item from my ArrayList.