title: Option 'complefunc' not set
body: <p>I'm starting to use vim in working with java and I want auto complete function eclim does. But while using Ctrl+X then Ctrl + U a message on status bar appear that </p>
  
  <blockquote>
    <p>Option 'completefunc' not set</p>
  </blockquote>
  
  <p>What are the steps in to solve this problem? </p>